I sent my son to training specific to running the sixty. It improved his running technique. Plus he got stronger. He cut his time from 6.8 to 6.6. Added strength in college got him to 6.5.
Chances are a player isn't going to improve from 7.0 to 6.6 or 6.5. But improvement to 6.8 could change how he's perceived as a college prospect.