Unfortunately all too often coaches provide well thought out solutions for something that is not really broken. On the other hand you need to be open to change as what works in HS/TB may or may not work that well in college. My DD is currently going through a process where they are refining her pitching mechanics and as a result she has lost some velocity (-5mph). However, her command and movement is more consistent and she knows that over time her velocity will return and possibly exceed what it was previously.
Nothing to add except in regards to the first sentence, yeah, I could tell you stories.