Isn't that one simply that BDD is about testing the functionality independent of how it is implemented, making BDD good for acceptance tests. And TDD is more about testing parts of an implementation to see that it does the right thing to implement the functionality, making TDD good for keeping on the path while implementing.

But yeah. Terminology within testing is quite messy. Some things are overlapping, different groups have different names for the same thing, and different groups have the same name but for different things.