Elon Musk fired thousands of Twitter employees shortly after he purchased the company and said their talents will "be of great use elsewhere."
There's just something fucking hilarious about laying off employees, mocking them, and being sued for improperly firing them -- and then whining that your competitor hired them and that they have access to Twitter information still.
I believe this fits well under the "fuck around and find out" doctrine.
They're rarely enforceable elsewhere, anyway. They usually depend on intimidating people, since they're not likely to win in court for the vast majority of cases (which is why they should be straight up illegal).
It's fairly ridiculous. So long as they don't take company property with them from the previous employer, there really shouldn't be an issue. Patents should be more than sufficient to protect IP. If you're concerned about someone building on that patent independently, you should probably do what it takes to keep them.