So about 3 months ago someone on the HUDS.tf discord mentioned how their minmode shotgun didn't look like b4nny's. We dismissed it as having something to do with 4:3 stretched.
A couple of days ago the same guy who asked at the beginning realized the stock shotgun and strange one looked different in minmode.
I went to my friend Beletrix who is working on a Balance Mod (https://ktbm.kingo.tf/) and showed them the difference. He quickly figured out the issue was in items_game.txt which controls the attributes of each weapon from what I heard. It also happens to be signed by Valve so you aren't allowed to change it. https://imgur.com/a/552vNRn
The stock shotgun
"min_viewmodel_offset" "10 0 -9"
Every other version of the shotgun. This is the wrong one (Unique, Decorated, Unusual, Strange)
"min_viewmodel_offset" "5 -2 -10"
So for whatever reason, the two "versions" have different min viewmodel offsets. It was suspected this was a soldier only thing but that wasn't the case. Every single class which can equip the shotgun has the same issue. Afterward, he opened an issue on the Source GitHub here: https://github.com/ValveSoftware/Source-1-Games/issues/3584
Have fun not being able to look at your shotgun the same way and getting mad at Valve for making TF2 p2w :D
@ValveSoftware please fix.