Vec
There are several reasons why the hover would be high (compared to early 1127/Kestrel/ and typical Harrier ones).
Going back to the early 60s escape following an engine failure in the hover was problematical given the limited performance of non-rocket seats. So at a lower hover height it was hoped that you could survive a heavy landing if you stayed in the aircraft. Remember thrust does not decay to zero instantly in even the most dramatic types of engine failure. That was borne out by the first guy to have an engine failure in the hover a Marine who hit hard and flat and bent the wings up but was OK.
Again at that time handling was demanding and the further you were from the ground the weaker were the visual cues and the harder it was to keep control.
These days escape should not be a problem and indeed we are probably back to the higher the better especially with a device that is held up by a pair of props front and rear which could fail independently.
In any test/development flight you get the best data so far as hovering efficiency numbers are concerned by being well out of ground effect. I dont know where ground effect starts on the F35B but it is a 40000lb class vehicle so it shifts a lot of air downwards.
As to quality of touchdown a good vertical landing on the hard in my view is one that restricts time in ground effect and gives about 4ft/sec at impact. This looks AWFUL to an observer because the only velocity he notices is the vertical one. When somebody plants a conventional jet at 10 12 ft/sec we hardly notice this because of the 140 150 kts horizontal at the same time that is rather more obvious.
So all in all I would expect GT to have been at the briefed height plus or minus not much.
JF