That’s funny, when I first learned about the equivalence principle, my first thought was “of course!” I have always found it to be very intuitive. The great leap is being able to frame it that way.
(Note that the HP Chipmunk 9836 also had a scroll selector wheel in 84)
Most people are UI bigots. Once they get used to a first something, they expect everything to work that way and hate learning anew. They get stuck on keyboards, mice, trackpoint nubs, trackpads, trackballs, scroll wheels, or touchscreens and refuse to move on. Of course there are 'objective' performance tests for each including Fitt's test of accuracy and latency, as well as, cognitive load. I guess once you have a hammer, every screw looks like a nail.
So I'd be a bit careful with the "of course!". It may well be obvious only because that is the first mental model you latch onto.