I think I should clarify here..........we don't have mountains in Raleigh. If you get up to your mountain descent speed, or really really long hill...........sure.
But here, the key is carrying speed up and over the next tiny little roller. There isn't enough time to reach a terminal velocity of any meaningful value before already reaching the rise of the next little tiny hill.
So, you stand to gain a LOT by flattening out the rolling hill instead of getting a 10 second "rest". If you can rest for several minutes due to a descent, I could see what you're talking about coming into play more than where I live.