While you very learned and clever chaps crunch your LaPlaces and Fouriers, to bring this back to the OP's question - from a piloting point of view- compressibility etc has no relevance on stalling. We are no longer in the days of Canberras and B-47s and in 'uncharted territory' but the driver nowadays has guidelines of 'normal' pitch attitudes at different altitudes and does not need to know or care about shock separation, and modern EFIS has buffet margins clearly displayed anyway. As long as he/she can differentiate between high-speed and low-speed buffet and carry out the appropriate recovery action, that is enough.