My (educated, I have used the mk4 seat for real) guess is that if he had tried to eject he would not have survived.
The Mk 4 seat in the T 7 is safe to use at ground level at 90 knots. However, a MB rule of thumb is,was that in a descent it needs additional height equal to 10 % of the Rate of descent. A quick calculation shows he was never within that envelope after reaching the downwards vertical.