@jack The principle I try to follow instead, which is more vague but covers much of the same ground, I think, is that the UI should feel solid. It should feel like a thing.
This, again, means no random flashes of white, no half-loaded content that jumps around, all of these makes the UI feel fake, and not solid. And, again, the animations have to make sense so that they feel like a thing moving around and changing shape, not loose part scattering. Solid.