I've been hearing that for years but the timelines don't match up.
IIRC, the reason the Disney people left is that when Animal Kingdom was being built, a land had to be dropped and Michael Eisner decided to drop Beastly Kingdom with the intention of adding it to the park later. The Beastly Kingdom team are the ones who left and I'm not sure when they did but by the time Beastly Kingdom was dropped, IOA had already started construction and The Lost Continent was already a lock in.