Dean's picture shows one with rubber band on it. It isn't disabled in the sense of a gunsmith disabling it.Mr Brownings first design did not have the grip safety. The US Army requested it.
That said I would never disable it
If one practiced with it like that I don't see a problem. If a person doesn't practice then yes I could see a problem.
Like @88E30M50 said a guy got hit in the hand and wasn't able to manipulate it that could cause major problems in a fire fight.