I think the only time it'll possibly go down to 10 Hz is if the Always On Display is on, since some people like to leave it Always on and 10 Hz would save lots of battery. It would be very silly if Samsung would lower the refresh rate to 10 Hz whilst the screen is on.
Yeah that would make sense. I've got the developer mode setting on at the moment and it only ever goes from 60 when the screen is still to 120 when I scroll or type. It re. ains at 60 even when you just stare at your home screen until the display turns off. I just read it can be set to 96hz somewhere that sounds like a decent inbetween.
I found this screen overlay widget in CPUWatch in developer mode which correlates to the FPS quite well. I watched a regular YouTube video and it said 30fps then i specifically typed for a 60fps and it showed 61. Though it goes lower, it went to 1.