I first heard about the old muscle memory issue back in the days when semi-automatics were the exception rather than the norm and the revolver was king. The point in contention was twofold; remembering whether you pulled or pushed to open the cylinder and remembering which hole to use if you had time to load just one round. I never really had to much of a problem with those and so carried both Colts and Smiths. When I changed though I did spend awhile practicing opening the cylinder and inserting just one dummy round to make sure it was under the hammer when it fell.
It was a different time I will admit and I honestly never expected to ever need to draw against another human; just as now I was not military or law enforcement, was not doing traffic stops or serving warrants or making arrests. I'm still not doing any of those things. I still expect that should I use my gun for defense it will be against a poisonous snake or threatening animal. There is a greater possibility than before of it being against a human but that still remains the least likely threat.
Today there is a different set of variations; safety up, safety down, lever hinged forward, lever hinged rearward, grip safety... as well as the variations that were part of the historical development of the semi-automatic. Grip safety that locks in the fire position until some separate motion unlocks it, grip safeties as well as a frame/slide safety, safety at upper rear left side, safety on left in front of grip, cross bolt safety, combination safety with one action for "Safe" and a different action for "Fire"...
Then there are the variations on magazine releases; heel release push to rear, heel release push to front, magazine release in lower front grip strap, button magazine release in front of grip at top left side, button of left lower rear grip, pull down ambidextrous releases in front of grip ...
And all the variations for field striping and take-down.
None of the variations though are extremely complex and if a user spends just a small period becoming familiar with any one of the many possibilities they can likely master it. Just as I can walk and run and jump whether wearing Cowboy boots or Huarache sandals or Oxford shoes or Wingtips or Docksiders; I can operate any of my various revolvers and semi-automatics.