While I understand your point, I think people often make statements like that, not because they are necessarily true, but to express appreciation for coaches they have worked with. It is unfair to say he became great because of something a coach noticed that no other coach would have ever noticed.
It is great that he got along well with his hitting coaches... but it is much more likely that he matured as a hitter and figured it out. Guys do get better. Happens often with young guys, and sometimes even with guys who are a little older (in baseball years).