Apparently identifying speed limit signs is AP1-only, because it relied on Mobileye's technology to do that and Tesla still haven't implemented their own replacement for that feature yet.
It's more of Tesla can't because because MobileEye owns the patent:
Tesla AP1 cars also have it, but when Tesla dropped MobileEye in favor of their own system, they can't use it anymore.
That is THE meat and potatoes of the patent. Sign recognition. i.e. speed limit signs. I'm not a patent lawyer so I will not pretend to know enough of the scope.