Watching You While You Poop

I own 2 cats. Our oldest cat, Ull likes to sit on the shelf we have in our bathroom that's diagonally situated from the toilet. Sometimes he likes to stare at you while you poo. The look he often gives you is one of absolute disgust.

I'm guessing that maybe that's the look cats give to other cats when they see one in the act of relief. That or it's only reserved for us and our disgusting way of taking a dump.