Explosive legs aren't ever a bad thing in baseball. I'm not sure how directly the air attack program will correlate to the mound, but I do know it will corralate to speed if it does work (verticle jump and speed correlate).
I'm curious if your friend has seen results on the program?
I've read some well written reviews from people gaining solid height and speed. While at the same time I have read reviews that complain all the program got them was sore knees and joints.
I have a feeling the program incorporates atleast some form of plyometrics, which have become somewhat common in baseball for conditioning.