Itās not a coincidence thereās 30+ things from less than half of chapter 22 ACOSF that can be compared and contrasted to the Azriel bonus chapter. This is intentional writing.
In the same way that chapter 22 was a Nessian part 2 for their previous encounter in chapter 19, the crumbs are crumbing that we'll get an Elriel part 2 resolution to their encounter in the Azriel bonus chapter.
ch22: Cassian is happy for Rhys
bc: Azriel is happy for Cassian and Rhys
ch22: Azriel tells Cassian "it doesn't matter what I want"
bc: We see Rhys enforce this later in the BC
ch22: Cassian's thoughts "of him and Nesta against the wall a level below, her hand rubbing him exactly the way he liked it, her moans like sweet music".
bc: While Azriel has thoughts of Elain "How that beautiful face might appear as he entered her, what sounds sheād make."
ch22: Cassian didn't see Nesta at dinner when he returns to the House
bc: Azriel doesn't see Elain when he returns to the river manor the morning after
ch22: Cassian is back because last time Nesta ran before after he was satisfied but before he could satisfy her. This time Cassian is the one leaving abruptly after satisfying Nesta (and leaving him unsatisfied)
bc: Azriel left Elain unsatifised and he runs off
ch22: Before Nesta, for Cassian "no female had ever come along whoād tempted him enough to fight for that future"
bc: Azriel can't resist Elain
ch22: Cassian has been holding out for the mating bond
bc: Azriel and Elain have only been holding off because of Elain's mating bond
ch22: Cassian "wouldnāt be able to rest, to focus, until he evened the playing field"
bc: like Azriel who is tormented by resisting Elain "Too many razor-sharp thoughts sliced him any time he grew still long enough for them to strike. Too many wants and needs left his skin overheated and pulling taut across his bones. So he slept only when his body gave out, and even then only for a few hours"
ch22: Cassian asks Azriel to "turn a blind eye, chaperone"
bc: Rhys is the uninvited chaperone, who doesn't turn a blind eye and interrupts Elain and Azriel
ch22: Nesta was "just getting to the sizzling first kiss in her latest novel when a knock thudded on her door"
bc: Elain and Azriel were about to have a first kiss before being interrupted
ch22: Nesta also hides the book "slammed the book shut"
bc: Azriel and Elain have to keep their interactions secret
ch22: "The handle turned, and there he was"
bc: "Soft steps padded from under the stair archway, and there she was"
ch22: Nesta's description of Cassian: "Cassian still wore his leathers, the overlapping scales of them full of shadows that made him look like some great, writhing beast as he shut the door."
bc: Az normally described in shadows, and in BC: "He aimed for the training pit, giving in to the need to work off the temptation, the rage and frustration and writhing need"
ch22: Nesta's in her nightgown her with her down
bc: like Elain with her unbound hair and venturing downstairs after going to bed
ch22: Nesta slides her book onto her nightstand
bc: Azriel keeps Elain's headache powder on his nightstand
ch22: Nesta's hair "slid over a shoulder, and she saw him mark that, too. His voice was rough as he said, āIāve never seen you with your hair down."
bc: "His head went quiet. But he took the necklace, opening the clasp as she exposed her back, sweeping her hair up in one hand to bare her long, creamy neck."
ch22: Nesta's hair "the gold amongst the brown glimmering in the dim light"
bc: Elain's "The faelights gilded Elainās unbound hair, making her glow like the sun at dawn"
ch22: Cassian describes Nesta's hair: "It's beautiful".
bc: Elain's describe's Azriel's necklace: " āItās beautiful,ā she whispered, lifting it from the box."
ch22: Nesta swallows under Cassian's attention
bc: Azriel has a similar affect on Elain "She halted, her breath catching in her throat. āIā¦ā He watched her swallow."
ch22: Nesta describes Cassian by the door "As if he were physically restraining himself."
bc: Azriel also is restraining himself, "Elain bit her lower lip, and it took every ounce of Azrielās restraint to keep from putting his own teeth there.", etc
ch22: Nesta scents Cassian's arousal
bc: Azriel can't stop the change in his scent and then eventually scents Elain's own arousal
ch22: "His scent drifted to her, darker, muskier than usual. Sheād bet all the money she didnāt have that it was the scent of his arousal. It set her pulse hammering, careening so far off the path of sanity that she scrambled after its vanishing leash."
bc: Azriel also has to leash/reign in his reaction to Elain's scent "Her arousal drifted up to him, and his eyes nearly rolled back in his head at the sweet scent. Heād beg on his knees for a chance to taste it. But Azriel just stroked her neck again."
ch22: Nesta "didnāt dare look below his waist. At what strained against his pants"
bc: "Azrielās cock strained behind his pants, aching so fiercely he could hardly think. He prayed she didnāt peer down."
ch22: Nessian: āWhy are you even here? You made it clear enough that last night was a mistake.ā
bc: "Forced himself to say, "This was a mistake.""
ch22: Cassian "Iām here to settle the debt between us." / ""The one I owe you for last night.ā He spoke as if there was no room in him for teasing, for humor.""
bc: Elain runs into Azriel to give him his gift - a gift with humorous and teasing intent and note that makes Az laugh
ch22: Nesta asks Cassian "Won't your friends tell you this is a mistake?" and Cassian responds "My friends have nothing to do with this. With what I want from you."
bc: "Rhys vanished, and Azriel was left standing before Elain, who still awaited his kiss. His stomach twisted as he pulled his hand from her hair and stepped back. Forced himself to say, āThis was a mistake.ā"
ch22: "The only mistake was that I came before I could taste you."
bc: "He needed to know what the skin of her neck tasted like. What those perfect lips tasted like. Her breasts. Her sex. He needed her coming on his tongue ā" and "Her arousal drifted up to him, and his eyes nearly rolled back in his head at the sweet scent. Heād beg on his knees for a chance to taste it."
ch22: For Nesta, "Breathing became difficult."
bc: "The faelights gilded Elainās unbound hair, making her glow like the sun at dawn. She halted, her breath catching in her throat."
ch22: Cassian "was trembling"
bc: "Elain shuddered, drifting closer. So close one deep breath would brush her breasts against his chest."
ch22: Nesta's "head emptied out"
bc: Azriel "His head went quiet."
ch22: Nesta "couldn't bring herself to deny him. Deny herself"
bc: "But he could have this. This one moment, and maybe a taste, and that would be it."
ch22: Nessian: "Just for tonight, sheād allow it."
bc: "Just this taste in the dead of the longest night of the year, where only the Mother might witness them. "
ch22: Nesta ultimately answers "Yes"
bc: just like Elain "āYesā Elain breathed"