Your point is well taken. I was mostly referring to the self priming qualities of some paints. The UH egshell will bond to drywall as well, but as you pointed out, the sheen quality will sometimes be compromised.Yes I did that from 1986 to 1993 on the new houses but it was always flat paint on the walls. You can do it with flat sheen. Anything that has a sheen from my experience you'll have to prime it first.