Imagine if you will the drama of Yor and Twilight revealing their true selves. The shock and confusion they would have. The danger that they would be in from their enemies. The trust it would represent from them both. It’s a moment in the manga/show that is predicted from the moment you hear the premise.
Whether intentional or on accident it’s the peak of the plot. But imagine again, if you will, the possibility of either of them never finding out about each others other life. That fate conspires that operation Strix goes on for much longer or that they both separately choose to give up their lives as a spy and an assassin for their family.
The show started with the observation that people have hidden selves, things that they hide from everyone they known and trust. It isn’t a bad thing it’s just a fact that very few people are open books like that. What better way to show this then leaving their pasts behind and loving each other for who they’ve shown themselves to be.
If Loid let’s go of his mission and Yor her assassin-ing. Then all the instrumental reasons for their relationship fade away. Anya is no longer a tool Loid worries about needing to discard. She is his daughter. They can both engage with each other as people. Yor sees her abilities as a wife as important because they ,in her mind, keep Loid satisfied with their paper marriage and allow her to keep assassinating people.
If that fake marriage becomes real she can see past the need to improve herself to maintain a lie and improve and grow for her own sake and as a expression of love for her family.
Now I don’t think that the show will go this way. Partly because neither Twilight nor Yor seem that put off by their jobs and partly because Loid is fundamentally a character twilight is playing, this is reinforced by the show, and I’m not sure how much of Loid and twilight overlap. I’m definitely unsure of what they would do with Anya knowing.
The idea though that both of them choose wordlessly to each other to drop the facade neither even knew was there and face each other as people is incredible to me. That nothing forces their hand and what is important is not what they hid from each other, but how they love being who they are together now. That their past is incidental to the odd family they’ve become.
Also them “renewing” their vows to each other as a scene. Incredible.