4 star at UCF is different than 4 star at Alabama. 4 star at UCF is the top dog and expects to start right away and to play. See Richardson last year. If they don't play they are gone. Hence why many 4 stars at UCF will have little impact. Not as big of a chip on the shoulder to go out and compete for playing time as the 2 and 3 stars have. This isn't the case at top programs that consistently pull in 4 and 5 star recruits. Not saying that a 4 star can't reign it in and be a role player (see Josh Reese), but many times a 4* recruit comes with a 4* ego as well.
I think this is true in most programs. For us success has not been linked to star ratings. There is no doubt that getting the top talent is meaningful in terms of the ability to compete year in year out. But for UCF it has not been an indicator of who will a meaningful contributor. If your class is comprised mostly of 3 star talent then we have done well. If Frost had stayed we would likely have seen a small bump, but I don't think it would have been much more than in the 50s