I agree with you Catt and Brian, both. One thing we need to remember is that "shallow" or "deep" is all relative to each body of water. Some lakes I fish are 25' max so I would bet that most of the bass move into 2-8 ft to spawn. Whereas, like WRB mentioned, he has seen beds in 25' on deeper, clear lakes. In a lake with max depth of 100-150' or more, 25' could be considered shallow. In some of my water where max is 25', shallow will be pretty darn skinny.
And one certainly can't say "well bass are programmed to go shallow to spawn" because I know of lakes that are only 10 minutes apart; one has max of 30' and the other has 160'. The bass in one lake don't know what the bass in the other are doing, it's all relative to their own environment.