he wanted to say, and I agree with him, that single pos training is a lot quicker than you wanted to say. Speed of training between Lvl4 trainer and Lvl6 trainer is not enormous. It's noticeable, but in a long run. From experience I'd say 2pos training's speed is approximately 70% of 1pos.
Example: If you train OD 1pos for whole season (14 weeks) on a 185cm 18yold with starting sublevels at 0 (let's leave elastic effect out of this), you will probably get 8-9 pops in OD, 1 in DR, 1 in HA and one in ID. That's 11-12 pops.
If you trained same player 2pos, he will get 6-7 pops in OD, MAYBE one in DR and HA and probably none in ID. That's 6-9 pops.
Apply this to three seasons worth of training and you gain approximately 10-12 pops per player. It's true though you can train more players with 2pos training.