I'm on your side! Sure one should be able to tap the brakes occasionally at opportune times in the mountains But, when I was training, I had a trainer that would not allow me to touch the brakes in the mountains. If I did ever use them in the mountains he would come unglued and jump out of the bunk and SCREAM- GET OFF MY BRAKES- and don't touch them again. He said brakes are for coming to a complete stop- AND THAT WAS HIS FINAL WORD!
So, I had to learn to not use them at all in the mountains. When I got rid of him, and started soloing, I did what I thought was safest and less difficult by the occasional use of the brakes in the mountains- AS NECESSARY! Which was not very often.
As I said- the Rockies are not the Poconos! Descending down a pass in the Rockies can go on for 12-15 miles of switchbacks with sharp curves and the grades are often very steep.