What does this have to do with talking about math? Title is rather misleading.
Professional engineering is as much 'talking about math' as performing legal services is 'talking about words'.
Both need a license if you're doing it for a living. Neither needs a license if you're just shooting the shit, and don't try to put the profession's weight behind you.
In this case, though, this was closer to political, rather than professional speech, and ended up protected.
So “talking about words” is a subset of a larger requirement.