When I last looked, it was described as an airshow, and marketed as " a pure aviation rush", so maybe not quite so obvious that a spectator should expect groundfire and explosions.
That said, I am inclined towards the same view as you, that if Police Scotland have acted for the reasons I suggested, this is very much "nanny state" On the other hand, neither you nor I are having to sign off on the risk assessment to allow this event to go ahead, but I suspect those who are find themselves in a very risk averse frame of mind following recent events.