36 minutes in one position gives roughly 50% of full training in one position training. I very much doubt that 48+ would five more rhen rhat in three position training.
At which point it then comes down to the other players involved - if the question is about the third trainee but the two main ones got 48+ and the guys playing the other two positions are old and wouldn't benefit from training, it's definitely the one position. If for some reason there are a bunch of trainable guys at all three positions who would all benefit from the training and the 1 position minutes for everyone are screwed up (and two position isn't a better option) I could see the case for three positioning. I think in most cases two positioning should be the fallback from one, though .