When processing the %files list, if a %doc file is missing you get an error message, but the packaging goes on and rpm exists normally. The resulting package contains all %doc files mentione before the one that's missing, and doesn't contain any %doc files mentioned later. Silent failures are no good!
FWIW, the silent failure has been considered a "feature" in legacy releases of rpm. I'm gonna dupe this bug onto the lack of scoping for %attr across %doc, as the solution to both bugs will be the same (i.e. rewrite a tighter copy of %doc files). *** This bug has been marked as a duplicate of 3230 ***