Yeah it being on Fangraphs now is going to cause a lot of people to misuse it, I think
For any established pitcher you don't really care about it that much unless you are trying to analyze a change (new pitch, injury, etc.)
It also has many admitted flaws. It struggles with changeups, for one thing, and that has a particular relevance for Luis Castillo.
I think Castillo's fastball does not actually have a great "shape" and he is a guy who derives a decent amount of effectiveness from command, also.