The realisation Crowley brings back from Heaven is "No wonder Aziraphale likes touch". He's seen how Aziraphale has made his bookshop into the opposite of Heaven - warm, cozy, and cluttered, where Heaven is cold, bare, and isolating. He just hadn't connected that it was personal as well.
And touch is the one thing he can't offer easily.
He would touch Aziraphale if he could, but it always feels like static electricity sparking and crawling over his skin when he touches anyone, and that in turn kicks in his snake reflexes. Snakes, he's discovered, aren't big fans of touch either. They recoil from it and coil in on themselves defensively.
It's easier when he's the one reaching out. He can brace himself for the sensation, because he's expecting it, he's chosen it for that moment of contact. He's learned to cope with hands touching when he must, for handshakes and the like. He got through holding the Antichrist's hand at the end of the world - though maybe all those years of holding Warlock's hand through gloves helped there, he isn't sure. Maybe it was just the sheer blazing adrenaline surging through his human body after all.
He does, however, know that wearing Aziraphale's body is like being touched all over, all the time and he hates it. Pretending that his skin doesn't feel as if it's about to crawl right off him drains all his energy, and on top of that, he has to pour more effort and energy into acting like his angel too. It's to save his angel's life, he reminds himself, and for that he will do almost anything.
Only afterwards, back in his own body, back in the Ritz again, does he realise quite how drained and exhausted it's left him. He sags into his chair, one arm hooked over the back to keep from sliding off completely, and he's slow to respond when Aziraphale starts talking.
They toast and eat and he tries to listen as Aziraphale rambles happily on and doesn't, thank Someone, try to touch him in any way, doesn't even try to goad him into initiating, only places his hand close on the table like an invitation Crowley doesn't take up. His angel doesn't push and that feels like a balm on his poor skin and heart.
"Oh, go home and sleep for a week," he quips, only half joking, the one time Aziraphale asks what he's going to do next, and that seems to be enough.
At least for now.
The realisation Aziraphale brings back from Hell is "No wonder Crowley hates being touched". He's seen how Crowley has made his flat into the opposite of Hell - open, clean, and stylish, where Hell is damp, cramped, and grimy. He just hadn't connected that it was personal as well.
Because Hell is also a place of constant jabs, pokes, prods, and shoves as the demons move through crowded passages. Every touch must remind Crowley of being down there, in a place that hates him, and that he loathes in return, and Aziraphale will do almost anything not to inflict that on him.
And yet he craves touch so badly that he isn't sure he can ever give it up entirely.
He's learned to soothe it by himself as much as he can, with snug waistcoats that put pressure in just the right places, tight wrapped blankets and one hand clasping the other, but sometimes the ache to be touched by someone else gets too much. Sometimes he can't stop himself from goading Crowley into body-slamming him against a wall or a shelf and just soaking in all the contact of it until Crowley runs out of things to snarl at him. Sometimes he can make do with Gabriel's careless shoulder claps along with human manicures and haircuts.
None of the other angels seem to have this problem with touch, so he ought to be fine. He shouldn't need it. But then again he doesn't need sushi either.
And even now, at the Ritz, giddy on survival, he sees himself reaching out to Crowley, closer than he ever has before, and makes himself lay his hand on the table, not that thin black-clad arm. Crowley does so much for him, it's the least he can do in return. It's enough to touch gazes so openly, he tells himself.
At least for now.