People argue that "skeuomorphism" isn't the right term for slapping photo textures on everything. It might not be, but obviously "realism" is an even worse term. Leather, chrome, or paper background textures resemble nothing "real" about showing weather forecasts, emails, or search results.
(That isn't to say good design can't use photo textures, but even many of the better examples tend toward the overblown "realism" of CD-ROM software from twenty years ago.)
A flat sink is a flat sink because it is flat.
A flat design is a flat design because we call it "a flat design."
Skeuomorphism isn't realism - pixels are pixels not leather.
A gradient isn't a shadow.
The flat "add comment" button below does not cause me confusion.
Curving a surface doesn't necessarily make it handle liquid properly.
A poorly designed urinal will splatter if hung too low on the wall.
And speaking of urinals, rounded corners and drop shadows do not make the image of a button art, unless perhaps one hangs it on the wall.