While looking at the altitude graph given by FR24 we should assume that data received by different ground stations is exactly what aircraft sent. Also there is no question about 4 station suddenly loosing correct timing.
Thus we see exactly what aircraft altitude sensors registered. If we speculatively exclude possibility that there was some electromagnetic disturbance that invalidated analog signals from altitude sensors, then these pressure fluctuations were registered at altitude sensors. One thing that could cause such a crazy fluctuation is an unusual attitude of altitude sensor port regarding airflow.
Also, sensors and computers and transmitter still had power and plane was still almost in one piece despite crazy attitudes.
It could be that there is not much useful data on CVR and FDR if breakup started from tail part.
Huh... now I speculated enough and have to stop