A bullet spin fastball will be hit hard unless it is 5+ MPH faster than the average pitcher at each age group. In college that would be 70+ MPH. Great pitchers have a blend of speed and movement. They can also hit their spots. A 60+ MPH fastball that a pitcher can locate on all 4 corners of the plate and mix in an occasional change-up can be very effective. A lot of pitchers can also vary the speeds of the same pitch to help keep the batters off balance.
Why do you suppose that is? We have a very popular pitching coach in our area, and her bullet spin is getting girls signed at the D1 level. Are you thinking they are not as good at lower locations? I have one of her girls throwing 56 with very few pitches in her bag, and she is doing reasonably well against righties at high level 14U.