I think it unlikely that its a hyd fail as the accumulators have enough energy in them to give 3 1/2 full aileron or elevator deflections before loss of pressure. So if the pilot gets a sniff of a hyd failure warning during aerobatics he would 'throw it away' and return to level flight.
The vapour trail is interesting but it could be a small fuel purge and happens a long time before the final manoeuvre. If it was hyd fluid leaking I would expect the aircraft to have warned him way before the final manoeuvre. Again, it would have meant a 'stop, stop, stop' at that point.
For JFZ90 - yes gate heights vary by type due to the physics of speed, weight, G, AOA allowance, drag and other factors. So it will be different between Typhoon and a Hawk.
LJ