i disagree but it is for advanced users only
sometimes you may have a real stud who you want to make the best player possible, maybe even national or u21 team standard
so 100% of your training will be based around this guys needs
for example if your guy is a pf you will mostly be doing is, id and re obviously
however you may want to give him a little passing and js so i think it would be fine to play him as a guard for that training until he pops
however maybe i am just being picky, 99% of the time choose one position and train that