It seems that kdeartwork-kworldclock depends on kworldwatch, therefore merging kdeartwork-meta (which is convenient, at least for me) causes kworldwatch to be pulled in. IMHO the artwork package should be pulled by the app ebuild, not the other way around.
I don't understand what you mean with "the artwork package should be pulled by the app ebuild, not the other way around". kde-base/kdeartwork-kworldclock needs (rdepend) kde-base/kworldwatch in order to be able to work. The duty of kde-base/kdeartwork-meta is to bring up all kdeartwork-* packages.
Sorry for bad wording :) I mean that the artwork package should depend on the application, not the other way around. My (parhaps flawed) reasoning is that I need (must have) the graphics if I have installed the application, I don't necessarily need the application because I have its graphics. The ebuilds may have sound reasons to work the way they do which would contradict my theory. In that case, simply close the bug report :)
Someone who uses kworldwatch does not necessarily want the artwork package. Simply don't use the kdeartwork-meta package, but install the individual ones.
