IDK why this is downvoted; it’s literally the zipper that causes this bulge by being stiffer and less likely to bend like the rest of the material used for the jacket/hoodie/pants.
At least on a jacket or hoodie, you can push it up so the bulge is on your chest or something. Can’t really do that with jeans when the zipper is just on the crotch.
I really want to check that out, but it is incompatible with my favorite mod: Save Our Ship 2. I refuse to give up SOS2 just to play with another human.