Rant:
That's social media for you love. Angles, lenses, poses, Photoshop etc. all models do so but he still has a big butt and the evidence you gave doesn't mean it's a 100% fake. His butt is Actually muscular as well. So I'm more inclined to believe it's real though not ruling anything out because I don't know him personally. You can believe what you want but he's still hot to me fake or not!
These pictures legit don't even look that disproportional to me. I can upload pictures of str8 bodybuilders with this proportion and I know for a fact theirs is not fake so this is not all that unreasonable. Unless the only people you're around or follow are as flat as a surf board.
Also different people have different body(types) and focus on different things. Isn't diago g4p he probably doesn't care about having a huge butt.
On the contrary look at josh Webster probably even more"disproportionate" because he heavily focuses on glutes. And I believe less than 5 years!. You can train different muscle. If you only do arms they'll get huge while the legs are scrawny. Because quite frankly that's just how muscles work.