ME did have some difference in body types of male human squadmates, Kaidan was quite regularly guy with muscles, Vega was huge bodybuilder, Steve was more in lanky, but still muscular side and Joker was quite lanky as well. But I'm all for different body types- hopefully for female characters and protagonist of both sexes as well.
Steve, Kaidan, Joker and Shepard all use the same body and armour meshes as each other. Only Vega is unique and even then his default armour is the same mesh as the N7 Defender armour and he uses the same Cerberus Ajax armour mesh as Shepard for his alternate armour. His From Ashes armour is the same mesh as Kaidan's but in a different colour. Joker is always in the Normandy uniform, as is Steve unless you romance him and that is the same mesh used by Shepard, Kaidan, all the crew and alliance personnel on the Citadel, the kids at Grissom and the Cerberus scientists on Gellix. There is a skinny version of that mesh which I think some of the kids might use but I've never noticed it in the game.
I'm not saying this to point out that you are wrong, just that you can think something is different than it actually is. I do it too. I always feel that Steve is taller than Shepard and Kaidan is a couple inches shorter even though they are all the exact same height.