Yes, and that's the rub. I've had several recruiters respond with, "oh don't worry, that's not enforceable" when I objected to an onerous NCC in a contract they presented me with. My response was "perhaps, but you could use it to drag me through the courts and make my life hell, so remove it altogether, or we're done here."
In each case, it was after I had verbally accepted a verbal offer. And in each case, they removed the NCC.
But you might not ever get there. In my experience, nasty employers will directly contact and threaten the employee's new employer, which can result in the employee being fired (or maybe never hired in the first place).