it was inevitable that aziraphale and crowley would reconcile almost immediately upon seeing each other again. their anger dissipated so quickly, as it always has, because the issue is they’re not actually upset with each other, but at their circumstances. deep down they both want the same thing anyway, so when it comes down to it, they always end up on the same side again. no matter how bad the fight, no matter the depth of the wound… they forgive each other.
take their reunion, for example. from the very moment aziraphale realised crowley kept his bookshop safe for him, there was no argument to be had. he softens, you can see it in his face. he lets go of his pride and anger immediately, and after crowley’s admission, he just seems… sad.
and on the other side of that, aziraphale sneaks his way back into crowley’s heart so sweetly. he asks if crowley wants an apology and saves his bentley and tells saraquel when they’re in heaven that crowley is authorised to be there whether they like it or not. by the time they’ve left heaven crowley is back to his old tricks, tempting aziraphale with food and buying him dumplings even though he’s still incredibly hurt.
so I think the reason crowley stops aziraphale from doing the apology dance is because there is nothing left to forgive on both sides. crowley spits out “I forgive you” to relieve aziraphale of his guilt, not for his own benefit. that’s why he is so embarrassed when says, “come on, angel”, because he and aziraphale both know he is already forgiven.
so a huge romantic declaration or overblown apology would not work in terms of characterisation, because they know each other so intimately. the issue has never been love or forgiveness. by the time crowley has saved his books and aziraphale has given crowley holy water, they are well aware of what they mean to each other.
instead, it’s about choice. choosing to be together against the odds, or choosing to argue, or choosing to run away. the issue has always has been “how do we navigate this fucked up universe?” and they have conflict because they can’t agree on an answer.
but the thing is, beneath their disagreements they ultimately want the same thing, and that’s to be happy together on earth, and a fair universe where there are no angels or demons to intrude on their happiness. so of course, there is no need for an apology.
they are always forgiven. that’s what’s so lovely. that’s why they look at each other so sweetly after crowley says “I forgive you.” god may not give them the mercy of forgiveness - but they can give it to each other. they can love one another unconditionally. that’s the whole point.