Perhaps I am just "denser" than most (and I'm talking body mass, not brain mass....though perhaps a case could be made for that too

) but I didn't find myself particularly floaty in the wetsuit.
I certainly would not count on it to make me a better swimmer/less likely to sink. But that's just me!
I totally believe what you are saying (about them providing buoyancy), but I, personally, didn't find that it made any significant difference.