Alpha prot is a function of Mach. No valid airspeed - no alpha prot. Latched.
Not entirely though. Because there is a maximal alpha prot for the low machs, and they could take this one into account even with lost airspeeds, i.e. they could have limited the trim up say up to 14 degrees AOA as is the case for low speeds. Granted you are still stalling, but not as badly.
It's like, say, assume that you don't have the slats and flaps position sensor. Yet, would you remove the load factor protection because the limits are a function of the position of slats and flaps? You can still take the worst case values, that shouldn't impact maneuverability.