I mostly agree with this.

Like, I know what a secondary dominant is because I've had to use it in blues turn arounds- I didn't know that's what some folks would call it, but I knew that in the key of G, I'd often play an A instead of the Am.

And I think that the vocabulary should describe what folks do rather than the doings being driven by the vocabulary.

Most guitar players (and improv folks) that I know have much more theory that the folks who are reading but who generally don't think about what the function of their line is in a larger song.

If you're playing by memory and ear, you have to have some concepts because you can't just read a part.

Those concepts -are- the theory.