I have a guy who is a good jumpshooter who reliably shoots significantly better on contested jumpers than on open ones (sample size of over 2 seasons, always plays as a G or SF so no position funkiness, discrepancy is 80-147 for contested vs. 62-148 for uncontested). Meanwhile, I have guys with far less JS who shoot a much higher percentage than that on open jumpers, but less well on contested ones, also over roughly the same number of shots.