FWIW the DI that taught a much younger me to shoot a 1911 subscribed to the thumb down method. I've never experienced, nor have I ever observed someone else experience, the thumb accidentally engaging the safety thingamabob. YMMV.
The 1911A1 service pistol came with a safety identical to this one:
this is a picture of a genuine pre A1 model, WW1 issue Colt. The 1911 model has an even smaller safety, and notice also, how short the issue grip safety and wide the hammer spurs. The gun was designed to be thumb cocked, and the grip safety was out of the way, and the hammer spurs were wide to facilitate thumb cocking. Original 1911s are so expensive that it was cheaper to steal the picture instead of buying the pistol.
I suspect the pistol you trained with was close to the configuration of the first pistol. However, post WW2, Cult Cocked and Locked modified the 1911 so they could play quick draw “combat” games. Fastest man wins. If you remember the pistol in the service, there was very little need for quick draw games, and the issue holster was clearly not designed to win “walk and draw” competitions. An issue pistol was carried in the issue holster and that was hung low on a web belt, and the holster had this monster flap.
Cult Cocked and Locked has modified the 1911 beyond anything that John Browning or
MG Crozier would recognize. And so, you have these huge safeties, that if propped with a 2 X 4 , could double as a diving board! The lever advantage of an extended safety, is such, these things are easily bumped in either direction without the shooter knowing. And there is one final indignity, occasionally the holder of the weapon forgets to take the safety off his cocked and locked weapon!
4 Reasons I Don't Trust The 1911 with my Life
I did take a Thunder Ranch class and the instructor made us “ride” the safety. This is prudent if someone decides to carry one of these quick draw optimized, 1911’s for self defense.
Another modification that Cult Cocked and Locked has made to their 1911’s, is that the beavertail has been modified so the pistol rides lower in the hand. Take a look at this 1911, with a “high” beavertail
And this pistol which has an early Clark beavertail
I removed the Swenson ambi because the thing kept on being bumped to the "fire" position, and it was this, that lead me to question the doctrinal tenets of Cult Cocked and Locked.
This Clark beavertail was made so the shooter could hold the hammer down, with his thumb, with the slide back, as the slide stop was released. This was a common safety practice back in the day when NRA Bullseye Pistol was the dominate pistol competition. Hammers and sears were typically military surplus, and honed to a light, no creep trigger. Unfortunately, these parts wore, and occasionally the hammer would follow the slide down. Holding the hammer back prevented discharge on the load command. Similar to the military configuration 1911, the Clark grip safety places the thumb below the safety. Modern beavertails place the hand so high, that the thumb is right at safety level. Incidentally, the hammer cannot be held down because there is no room between the hammer spur and beavertail. Because the thumb is so high, an extended safety must be ridden, because it is so easy to inadvertently bump the thing in either direction. The shooter won’t notice until it becomes apparent, that the gun is not going bang, and from there, there are multiple failure modes that have to be explored before the correct failure mode is determined.