Well, I think the FG perception is that a mid-rotation starter prospect (#3-#4) like Crow can bring back a quality set up guy. By their rankings, I think Crow is a 45. Garcia is thought to be an average or better major league ballplayer, and that is thought to be worth more. Putting a Garcia and a Crow in a package for Yates, Dyson, Giles, and others of that quality should get you the pitcher plus something, at least according to their view.
For Crow, I think a #4 is his floor, not his ceiling.