The TUNECONFLICT value is not documented, and at least a couple of tunings spell it TUNE_CONFLICTS.
This bug is for me (post 1.2 freeze)
It also has no code actually making it do anything although it was discussed at the time we implemented the tune code. We need to add that code.
Seebs has been working on the solution to this issue. A preliminary version has been sent to the mailing list already. Estimate is to finish the work.
Checked in to OE-core commit: 6ffe53c721a80cf156b44f59b564f2e899c6af50