It’s a little know fact the umbrella brand healing liquid is also a fantastic garment glue.
I don’t make much of the jacket thing. Ethan’s healing abilities are vague at best, he can survive having his heart ripped out Kano style but he can’t regrow two fingers despite dousing them with healing goo all the time. I also don’t make much of the fact that no one else in game uses it. Jack taunts Ethan by giving him a bottle when he cuts his leg off to reattach it. When you play as Mia in 7 she uses it and it’s obviously everywhere as you find it lying around in both Louisiana and fake Romania. It’s just a game contrivance thing. It’s why the game has bullets and shells everywhere but no one uses a gun, even Heisenberg’s huge metal army is all melee weapons.
The sleeve bit I chalk up to two things, one it was probably way easier to not make a second model and two, it’s just funny. I cackled when his hand went back on sleeve and all, it’s just so silly. There’s no way the people who animated that didn’t know it was going for humor. The jacket thing to me was just a nice touch for Rose to show up as an adult wearing the same jacket. Also hey, dude is walking to his grave and it’s cold as hell, the baby needs something to keep her warm.
Narratively it just gets too weird if his clothes are his body. I can just barely buy a world where Ethan doesn’t know he’s living blue cheese and somehow creates viable sperm but I’m sorry I can’t buy a world where Ethan just automatically generates his clothes off of his own flesh and doesn’t know it. Ethan my have a vacuum between his ears but even he would realize that’s he’s never bought a single piece of clothing and that when it rains he just suddenly has a jacket. Besides if we believe the figure in the epilogue is actually Ethan and not capcom trolling he clearly didn’t need the jacket to regrow himself.