Dozy,
I agree with you about the designers --there was no reason for them to foresee a need for a stall warning below 60KTS. And if they had, presumably they would have chosen a technology that was reliable below that speed.
But if you're saying the stall warning should be suppressed below 60KTS because the airspeed data might be wrong, I don't agree. No matter what the pitot tubes are reading, the airspeed is either over 60KTS, in which case the AOA sensor is reading correctly, or it's below 60KTS, in which case the aircraft is stalled regardless of what the AOA sensor says.