[dcb]

when making a human use a single speed, that human cannot maintain their most efficient rpm and load. In and of itself the derailleur ads a tiny bit of drag, but on the road the gears allow the human to remain more efficient, which probably falls off exponentially vs a constant slight drag from the idlers. That is how it is not max efficient.

Besides you are looking at a restricted class of one hour racing, on a bike from 1972. Which is only running on a track at a constant speed, yadda yadda.