Even if a person falls from "only" a 2m high platform because a guard rail is absent, they are not expecting to fall and will not be prepared for it at all. They will not have any warning or time to use their arms etc, to break their fall. If the fall is onto tarmac or concrete, head first with no warning, that will be extremely serious.
I hope the guy fully recovers, and a mental note to us all to take extra care and follow safety procedures - Safety First !
I don't know the circumstances here, but in hangars there are safety straps hanging from the roof for engineers working on the top of wings or the fuselage to clip on to. And I have seen in new houses being built that they cover the ground floor with air bags when the first floor structure is being put in, in case anyone falls from it. Not practical in aircraft maintenance, hence the roof straps. However, if the maintenance is being performed outside........