J. M.'s 1911 was designed without
a thumb safety. Like any pistol or revolver of the time, the user cocked the weapon for the first shot.
The thumb safety was added to solve the problem of lowering the hammer on a live round while mounted.
The grip safety was added at the Army's request. J. M.'s prior guns with grip and thumb safeties were hammerless (actually concealed hammer) guns that could not have the hammer lowered.
Oddly enough, the bureaucrats got it right that time. The cocked and locked feature of the 1911, and it's reliability, make the ultimate defensive sidearm.
DFBonnett, the military manual of arms for 1911s has nothing to do with firearms design. It has more to do with the military's attitude toward handguns and soldiers, to wit: "Handguns don't matter and soldiers are stupid."