Actually, they are unlocked during ascent and while accelerating, but only after the airspeed has reached Mach 1.4.
The general consensus is that Alsbury unlocked the feathers while the spacecraft was still in the transonic phase instead of after it had reached supersonic flight.
The buffeting of the shockwave is thought to have caused the feathers to prematurely move and aerodynamic loads caused the spacecraft to break up in flight.
So... had they been locked, this wouldn’t have happened.
Why do they unlock them ?