WHEN can we finally expect an AOA indicator in the flight deck?
That discussion finished when some smart engineers decided to place the engine and propeller at the front of the fuselage in the early 20th century, making a reliable AoA indication impossible.
This means in SEP initial flight training you do fly aircraft without AoA indication, so that becomes the standard of learning to fly. Very unfortunate, but practically impossible to change. A mix would probably be even more dangerous, than everybody relying on ASI...
So unless somebody develops a modern AoA Instrument which reliably works on all aircraft (e.g. a laser doppler anemometer based AoA indication or something alike) and can be retrofitted to all training aircraft, there will be no quick solution.
Back to topic..
Does anybody believe in the altitude dip recorded for both flights?
For me this is indicating an issue with the static pressure measurement. I think this dip in altitude 23:21:40 to 23:22 for this flight and at 14:25 on the previous flight is an error in the data, and not the real flight path.
Especially as the curve returns to an expected one after a short time with no remaining offset.
Failure which occurs spuriously can not be created by a covered/blocked probe, such failures would intensify with altitude.