I have no teaching or research experience. This answer is all guesswork. There's more than one way to take notes. One way is the proper way where a student happens to get their own natural desire to use their own method of writing things down based on what the teacher says and choosing which parts they're interested in picking out and remembering and with more experience improves their own method of writing down and interpreting what they wrote. The other way is the way I did as a result of my lack of understanding of why to take notes where I just copied down what the teacher wrote on the board and read it later. Maybe some other students did it the same way as me. I think the proper way actually can help as long as the person has the natural ability to do it. The way I did it on the other hand might not help.
I once heard somebody say that when he writes down what he reads, he remembers it better. That's probably because when he writes it down, he ends up reading it slower so it ends up easier to remember it. That doesn't necessarily mean that's the case for taking notes. There's a reason the first way of taking notes I described is better as I will describe later but not everybody has the natural talent for it when they're in high school so some high school students might adopt the method I used. When they take notes and don't have that natural talent, writing down what the teacher writes on the board doesn't slow down the lecture. The teacher is still talking just as fast and it's still just as hard to remember it. The teacher's writing on the other hand is slower so it should already be easier to remember so I'm not sure there's any use in copying it down.
I was also taught point form notes in elementry school and only way later did I figure out the real purpose of them with an understanding. I much later long after I was finished high school had my own natural desire to figure out how to explain things in an organized way that I probably would have figured out even if school had never tried to teach me how to write an essay in an organized way. It's basically planning ahead how to organize a message except my natural desire that just came was to do it in my head. Sometimes I write a bit then plan then continue writing more. Maybe a few times in high school, I had my own idea of how to organize a message for a specific assignment but I didn't get the marks for it. I think that schools are cramming too much material on their students and when they're taught too much, they learn less. That's because sometimes students cannot figure out why the teacher is saying what they're saying when trying to teach them skills and then struggle and then the teacher moves on before they're ready.
In addition, being made to struggle instead of using a student centered approach causes them to adopt a linear thinking approach and actually makes them less good at thinking their own thoughts and coming up with the idea of organizing a message and writing a plan for one on their own with an understanding. That could be another reason telling students to take notes in high school could be detrimental for those who don't have the natural talent to do it properly easily. I read on the internet that Finland uses a student centered approach and I also read on the internet that Finland has a really good education system.
Finally, another reason it could be detrimental to tell students to take notes in high school who weren't going to choose to. Maybe they already have more experience doing the creative thinking with their brain alone and it ends up better in the long run when they just continue their habits of finding it normal that they can only use their brain and have no written copies to get aided by in remembering the lecture.
There are totally different types of notes which can be useful. In my high school Environmental Management course, the teacher put up an overhead with text to write down in class. Maybe some people by writing it down are forced to read it slower so they end up remembering it better. Also in university, I had a statistics course whose textbook was very confusing but the teacher made his own power point notes to read online at home and I read them and learned a lot from them.