the motion of taking a SA safety, like a CZ, or 1911, is pretty easily made into reflex. As you bring the pistol to aim, its a very natural motion to drop the thumb. Given that the ubiquitous AR uses the exact same motion, there's really no reason not to get into the habit. "Gross motor skill for the aim, fine motor skill for the safety" is literally made up nonsense. If you can work a trigger, you can work a safety, and most 1911/CZ shooter do it instinctively. As for Decocks... I have never seen anyone recommend carrying anything other than hammer down, safety off. As far a holstering, if you've just been in a gunfight, and need to holster, you probably don't want your hammer down, and awkward safety on. Most advocates against SA are really against safeties alltogether.