It's not the same, which causes 1 G stall speed to be higher at high altitude even in IAS (in addition to being way higher in TAS due to the much more familiar density error).
We say that the wing always stalls at the same AOA when teaching/learning basic flying, but that's a simplifying approximation to make the basics easier, or a "lie told to children" if you will. It's true
enough in the envelope of a piston trainer. But compressibility (Mach) and viscosity (Reynolds) effects change the air flow behavior even at the same AOA, and cause an earlier (i.e. lower AOA, higher airspeed) stall at jet altitudes.
