Rationale: Allow the same meta layer to be compatible with multiple Yocto versions, with duplicate recipes skipped when versions from newer Yocto is available or blacklist recipes that require newer Yocto versions. Putting the yocto version string into OVERRIDES would be a welcome addition too.
I can see why this would seem like an attractive idea. Unfortunately this is not a behaviour we want to encourage though. We need to make it clear which versions of core are compatible with which layers. If we supported something like this, it would imply that may different branches could all be intermixed and expected to work and we'd end up in a mess. Its a sad fact that users already struggle with layer quality, intermixing things that work out as untested and incompatible. Also consider that newer versions deprecate and remove functionality (like file:// url globbing) or will rename variables for the inclusive language changes we have that are coming up. As such whilst technically possible, we probably should go in this direction.