Been shooting for many years, and will disagree with you there, here is why:
Never saw anybody improving by using this method.
Shooting isn't rocket science, you lined things up and fire. Simple.
You can test shooters with just one round in the magazine, if they suck, they will suck with 22, with 9, with anything. With one bullet in the mag, the whole recoil argument is moot as there isn't a second shot, you first shot is gone, you sucked, game over, when you felt the recoil the bullet was long gone.
Bad shooters have preconceived fears (this is gonna blow up in my hand), anticipate recoil, twitches, squint, poor stance, poor muscle strength, poor posture (seen really good shooters with bad posture), bad hand eye coordination... Some people just can't. The caliber has ZERO influence in their competence for that one single shot.
If you cannot control a pistol, you need to workout and get stronger. Understand what is it that you are doing to improve. I am 1.69 meters tall (5.5ish feet) dwarf and can shoot decently any caliber, typically top against in my area and very close to other shooters that are nationally known. Not gonna give names lolol, In a nutshell: It is not about the pistol, it is about the person holding it.
No. You are looking at it all wrong. 9mm is the better option for individuals who are not a good shot, as it easier to learn to shoot decently. If they're already not great, why would you want to give them a gun that's harder to use effectively?
When someone asks "what should my first pistol be?" how many people say 9mm (or even 22lr)? Very few people recommend a 40 as someones first handgun.