The only thing I can think of did they have their HID ballasts located OUT of the grow area?
That would make a huge difference.
I ran an 18,000 BTU in room AC in a 4’ x 8’ x 7’ tall tent with 2- 1 k’s burning.
As an old box grower, you always remote the ballast OUT of the box!
My AC had plenty of cooling, as I never size to get by.
I always wanted a motorized item to be working around 3/4 capacity, over full blast.
Stuff just wears out faster, and you have more failures
This one unit, cooled 3 different tents, set up during summer, and still was only half running capacity.
I made a plenum and shuttle box to move air where every it was needed.
Worked a treat, until my LED’s made it worthless.