If Calta did 3 sets per exercise then he probably did the same amount as Mentzer. Mentzer just counted the 1st 2 sets as warmups.
Not exactly. He changed his workouts so many times. He won the Mr. America doing a whole body routine three days a week using a mix of Nautilus and free weights. He used two work sets and sometimes one work set. From there he trained for the Universe training four days a week. Monday was Thighs, chest and triceps. Tuesday was back, delts and biceps. Wednesday was off. Thursday was thighs, chest and triceps. Friday was back, delt and biceps. He did this for many years. Sets were two work sets or one work set depending on the exercise. His last change was using Calta's rotation training three days a week. Those workouts he described and recommended after he retired were nothing he every did and they were convenient to train clients. Train a client for 25 minutes then tell him I will see you in 5 to 7 days. He did train pure Nautilus when he was down with Arthur Jones for a brief period but his training always consisted of a mix of Nautilus and mainly conventional weights. Toward the end of his real training life he was seen using more sets. He rarely trained for over a decade of the last years of his life and it showed. I might own the most complete collection of everything he ever wrote when he was a competitive bodybuilder.
If a trainer is using free weight and training with HIT warm ups a necessary. He might use something like this.
Barbell bench press 1 x 10 135lbs
1 x 4 225lbs
1 x 2 275lbs
1 x 8 315lbs (That 8 rep is the failure set and the real work set.)
This person could legitimately say they did one work set for the flat barbell bench.
His next exercise could be the Incline bench
1 x 6 135lbs
1 x 4 225lbs
1 x 7 275lbs (That 7 reps were to failure. The one and only work set)
Next up could be flies 1 x 14 65lbs ( No warm up necessary because of the prior exercise)
Last up could be weighted dips 1 x 6 body weight
1 x 10 45lbs (This is the work set to failure)