Backpacker
I am just guessing
I suppose anything above FL55 and they consider that to be enroute to somewhere below could be taking aunt Matilda for an eyeball view of the power station.
The second reason is they have to show a law you have broken should a conflict ever occur.
Entering a restricted zone would be cited whether your an innocent PPL or a Greenpeace intruder.
But just guessing
Pace