Why limit one’s intake & creation of art by putting rules in front of it?
An artist always edits their work. In camera, by framing or in a darkroom by dodging and burning, carefully selecting film grain or camera straps.
Purists may ultimately not be artists at all by succumbing to their fears and latching onto a set of rules rather than facing the scary truth that they are more unlimited than they give themselves credit for.
In other words, putting a set of limitations on how another presents art is eventually an environment to grow out of or die trying.