any reason cum on ass doesn't implicate ass

Asking before I make the BUR, since it seemed obvious.

Maybe to encourage only using ass for when it's clearly visible. Doesn't have to be the focus, but maybe there are cases where you wouldn't want to tag it.

Similarly, ass visible through thighs, ass rest, ass support, and most things in tag group:ass don't imply ass. But should they?

Probably because of all the posts like post #9231463 or post #9226475 tagged with it.