The Gentoo Handbook contains a section about updating world which mentions: """ Dependencies are not part of the world file, but we will get to that later. """ There is however no "later". The phraze refers to the use of "--deep" to have "emerge --update --deep world" take all dependencies into account (instead of just the immediate dependencies of the world-file), but this isn't listed in that chapter.
This has been brought to my attention by Jake Ribnik (jribnik | oddly net)
Fixed in CVS.