It seems pretty basic to me - "If this were flattened, what would it look like?" In other words, pressing is most effective on rippling, bends, curls, etc.
It's "cleaning" that gets sketchier for me. Like, in a "clean and press," what are the limits of a clean? Getting rid of pencil? Pen? Grime? Light soiling? Food? Clearly not water staining. Do the insides get done? Is it "spot-clean," or does the whole thing get done, sometimes (key word: "sometimes") resulting in colors looking better, and whites whiter?