Well if your IS is much higher than the other elastic skills, it will train slower (effect goes both ways). So if I train my big with huge IS in 1v1 forwards, he will train slowly in IS. On the other hand, a guard with low IS that is trained in 1v1 forwards won't have the elastic penalty, and thus train his IS faster. In this case, it's not because 1v1 forwards trains IS faster for guards, but the data used is influencing the results.
So my question is more geared towards "is the data representative", would it show the same difference in training speed if players with the same skillset but different heights are trained?