The P12 once used the same loadout icon as the P9 in-game. In Update 3.2, the icon was changed to the proper one depicting the P12.
Interestingly enough, the P12 has a different firing sound effect when either playing as GSG 9 Operators or spectating/viewing their 3rd person models (in-game). This bizarre trait is shared with the Super 90 and the D-50.
Blitz's reload animation for the P12 is different compared to other Operators. Notably, when reloading from empty, Blitz presses the slide release instead of pulling the slide to chamber a round.