Rich_genie said it all perfectly, Determination is a great "free" attribute to have but it does nothing towards training. You want it high because players will usually perform better in games which in return helps them develop which is possibly why people presume it works for training.
Find someone who has an ideal personality(High professionalism is a must, ambition is a bonus) they also tend to have high determination, then just tutor him.
If you're still not happy about his determination then just find someone with high determination to tutor him first then have the better professional tutor him after.