Yeah, i think JF didnt know everything about this topic.On few occasions he was wrong,and/or not exactly fully truthful.
Seems like AM3+ chips will fit just fine in AM3 board physically, and as for the working, its atleast possible on some of them.
Im not sure AGESA transplant will be enough tho, seems like there are two pins which most manufactureres simply didnt connect on their AM3 boards.