Why no thumb safety?
If you train with the gun properly, you don’t need one. And arguably it gives one a small time advantage when going from holster to shots on target. One less step in the path. I have trained with but glock and 1911. I love the 1911 but the glock is simpler thus faster.
Almost all situations are not going to be throwdowns where who clears leather first wins. How long does it take to flick off a safety?