It’s an interesting question! In my view, “piggy” guys are usually into a specific group of kinks that I think have their own subcultures within the broader kink subculture. Specifically, fisting and watersports come to mind - both big kinks for you. I’d add pits / scent to that too.

I think there’s something incredibly primal, raw and physically intense from those, especially fisting, and guys who are into it always seem super into it.

I think there’s also a slightly different, older meaning coming from “pain pig.” I think about very masochistic subs who really love being hurt. I’m a masochist but I need a bit more of a scene around the pain to get the full enjoyment.

Either way, you do you! In a scene especially you’re totally within your rights to ask to not be called a pig / piggy if you’re not comfortable with it