This is exactly what I mean, though. You're asking someone who has done the same style motions for 16, 17 years to all of a sudden forget every single thing he's done and rebuild it. You're telling him to entirely change the mechanics that he probably doesn't even have to think about executing. I'm sure Lamar doesn't even realize how he's throwing.
It is NOT as easy as some people want to make it seem.
This is a bit of an extreme example and this is definitely not a 1:1 because this player had further issues, but think of Tim Tebow. He had a HORRENDOUS throwing motion and was horrible with his mechanics. But he had an AMAZING work ethic and an AMAZING attitude on the field. But he just never actually got any better. It is not easy to fix mechanics and that's one of the biggest issues in the scouting community.
Scouts see the amazing arm strength, the big body, the ability to run and they think they can just fix the throwing motion. That's easy to do they say. Well, turns out it isn't.