Sure it's really just TDD, but it's changing the semantics to encourage good TDD practices instead of just a verification mechanism.
I think you hit the nail on the head there. I've messed around with both TDD and BDD in Ruby, and, as you'd expect, neither seems to do anything that the other can't do.
BDD just uses different language in an attempt to encourage good testing practices. It's the kind of thing that's easy to downplay, but of course the only difference between any two general programming languages are the things that their syntaxes encourage and discourage.