I'm not totally sure, but I don't think the 'reduced functionality' has to do with the chipsets, but may have to do with the difference between AM3 and AM3+ in configuration of the power planes. Similar to the 'reduced functionality' when an AM3 chip is used on an AM2/AM2+ board.
If AM3 chips can work on AM3+ boards, but not the other way around, may suggest that BD is multi-plane only or works best on a multi-plane (more than 2) voltage board. Though, honestly, I don't know.
If AM3 chips can work on AM3+ boards, but not the other way around, may suggest that BD is multi-plane only or works best on a multi-plane (more than 2) voltage board. Though, honestly, I don't know.