I disagree with you that it is impossible for a child to learn immediately that it's unacceptable to hit other children. I grant you that it may be impossible if you use the medium of long conversations about feelings.
That just depends on the development of the child- as I said some will learn quickly AND have the impulse control to stop themselves, some will learn the rule but not have the impulse control (especially true for some neurodivergent kids), and some will just take time to learn.
It’s unfortunate that the ratios that are considered sufficient in child care settings are not necessarily in line with what children need, but again that is not going to change the biological progression of development. It just is always going to be a problem.
My son for example went through a hitting period, and he would usually do it after he had tried to hug a child who didn’t want a hug- clearly being driven by a feeling of rejection (rejection sensitive dysphoria is still a massive part of his adhd) but that doesn’t make it ok.
I am not an endless talker- the minute he began to raise his hand I was in there, lifted him away and said “You are NOT allowed to hit!” In a stern voice. Then he cried, and I explained, in short simple terms -named his feelings, what had caused them but why hitting is never ok.
If it happened more than once I took him home, because clearly he wasn’t able to control himself at that time in that space.
I probably had to go through this 6/7 times before he stopped- he never actually hit a single other child in that time because he was never put in a position where he was able to.