IANAL but as I was told by some who are:

They can say that all they want, but that isn't what the statutes or case law about trade secrets says. in California state courts take a very dim view of this sort of overreach.

That is exactly what I'm wondering about. At least a few states have severely limited noncompetes and even outright banned them in specific contexts. I have to wonder if a nondisclosure twisted for use as a noncompete would survive the courts in one of those states.

I'm also skeptical how enforceable this theory is in general. Have there been any noteworthy cases of employees getting screwed over that rested on it?