Math yeah, but the math is based on original and optimistic specifications, which I doubt have ever been verified. The same is probably true for all the resorts listed at that site. Nevertheless, Greek is a special case, those who work the hill, we know the lifts. The numbers are optimistic.
"Visions" Quad, the newest, at about 10 years old, is a refurbished system. It hasn't run
consistently at full speed since the day it was installed. Depending on who's talking, the reason is either because management is saving electricity or because the moving loading ramp is a poorly timed kludge, which either runs to fast or too slow for easiest loading. Whatever the reason watch both Chair 1 and Visions, and you'll understand why it's a employee standing joke that the old Chair 1 runs at about the same speed as the new supposedly higher speed quad.
As for the rest, they were installed 40-60 years ago. The oldest, 60 year old Chair 2, refurbished 20+ years ago, may be running
faster than original speed, but who knows? Then there is the 40 year old backside triple, whose motor is both problematic and perhaps the slowest triple chair I've ever ridden. Chairs 1, 3 and 4 were installed about 50 years ago. They are well engineered Halls, well maintained, but nobody knows if they are running at original speed.
The bottom line is that Greek's mostly antique lift system is well maintained, but its also slow.