User blog comment:Mich, Michele & Kuhla/Guide: UBB and the OD gauge/@comment-107.77.94.24-20150615203804/@comment-26454549-20150621153730

This only applies to 7* units only, 7* only get this ability. Even if you a unit with a potential 7* form. until it reaches 7* and has a SBB of 10 UBB wont appear.