I should be somewhat fair, I haven't had many instructors, and my instructors mostly glossed over the issue without saying much. I expect that they were following the SSI curriculum, with little deviation, at least for that portion of the class, and didn't want to deviate too far (not sure if that could affect their ability to teach).
I just felt I would have benefitted more if they had explained what I just stated. That it's not "wrong" to use your hands, and it can be useful. However, if you practice not using your hands and learn some finning techniques instead, you should be a LOT better off long-term, because if frees your hands for other things.
Speaking of which, none of my in-person classes or SSI online training has talked about finning techniques. I have however gotten some online-training from sidemounting.com, they have a few finning videos in their free section. My frog-kick & helicopter-turn sucks, but at least I know it and am improving.