Wilder is not wider, he is longer. He has long bones; a longer clavicle, arms and legs. But his bones are not wider, I would bet Joshua has a wider ribcage for example, and obviously thicker bones.
Only Wilder's collarbone is wider (more like it is longer), that's one bone. I would bet Joshua has a wider ribcage, waist, hips, wrists, calves and pretty much everything wider except for his clavicle.
Yes that's what makes him wider lol, longer as you put it. The width of his shoulders are bigger than Joshuas, more muscly though is another question
Anybody ever seen Joshua and Wilder stand next to each other? I wouldn’t be surprised if they were the same height, since Joshua has admitted that he’s 6’5.5”. I’ve met Wilder plenty of times and he isn’t 6’7”. He looked a lot closer to 6’5” to 6’5.5”. He was shorter than Carmelo Anthony, who I personally measured in 2001 at 6’6” and Carmelo was slightly shorter than Tyson Fury, who Wlad said looked the same height as 6’7.5” Wach.
There's more to size than bone structure anyway. Wilder can juice and do all the squats he wants, he will never have legs the size of Joshua's.