Okay, so you think it's a bit young as a method of behaviour management. In order to formulate a complaint that makes sense, can you articulate why using behaviour management that you think is a bit young, is actually a problem?
At present, what I see is a parent who has a different preference to your child's teacher.
The thing is - you don't know every child in the room, you don't know who or how many of them have anything like neurodiversity or learning difficulties, how they respond to instructions as individuals and as a class - because none of that is your business. You don't know what strategies this teacher has tried and found to not work, and you don't know if they have a plan (and likely experience) for changing how they manage behaviour as the terms progress.
If it's effective behaviour management, I'd stay well out of it. In fact I'd stay well out of it in every single scenario, apart from if you think it's significantly stunting your child's development. I think you'll probably agree with me that whilst you might think it's a bit odd and babyish, it's not even remotely harmful. In which case, stay out of it and chalk it down to not everybody will do things the way that you would.
I am really puzzled if you are a lecturer - have you not been in this type of role for long? Have you not had students and parents complain to you/your HOD/Principal with petty or nonsense complaints that you internally roll your eyes at, and wish they'd get a grip? This is the same. Don't be that parent.