It is sort of humorous, but the Army did insist on the grip safety so the gun would not fire if dropped, and that is the one case where the grip safety has no effect, since it only blocks the trigger, not the sear. The Army wanted the manual (thumb) safety so a cavalryman could make his gun safe when he had to control his horse. With DA revolvers, they could uncock them, but the auto pistol was then not ready.
Note that Browning put grip safeties on other guns, notably the 1903 pocket model, before government trials. Supposedly, that was to make sure that people used to revolvers did not let their hands ride up and get in the way of the slide.
Jim