Exactly. The early PADI Nitrox class was substantial....and I took mine in 1999 from Brian Kakuk.....lots of work with tables, equations, Equivalent Air Depth, O2 toxicity, NOAA O2 exposure tables....
I took the PADI Computer Nitrox class, and don't remember doing any calculations for the test. But after going back and learning what PADI didn't teach me, the things I wish PADI taught be better would be the equations for MOD, and the NOAA O2 exposure tables.