I always thought that if an ebuild is newer than one listed in package.provided, emerge should report this newer ebuild as an update. But that is not what happens on my system.
For example, if I put media-sound/wavegain-1.2.6, which is an older version, in my package.provided file, emerge -pvDu world does not indicate that a newer version, media-sound/wavegain-1.2.8, is available. The only message is that the package is listed in package provided and thus will not be emerged. So on my system, the ebuild version given in package.provided seems to be completely ignored. I suspect that this is not correct. Should a bug report be filed? Frank Peters