This is a convenient feature that worked correctly here although my KPA was set to tuner and the tuner bars stayed visible during the updating process.
EDIT: It didn't install the beta OS (checked System p18) even though it appeared to. The update beta OS is not available separately for USB install and RM is not doing it. Suggestions?
EDIT 2 - Solved, so as not to repeat please see other thread discussing where pure cab is discussed and I'll post my experience.