Not really sure what your point is by asking how many impact freshmen we have had in this circumstance. Ther will be freshmen with impact, depending on what your definition of impact is.
My point is that most impact freshmen - freshmen who lead their teams to immediate collegiate success - have impact because they have the talent and physique that allow them to excel against bigger, stronger, older, more experienced players, and the maturity to overcome the adjustment between high school and college. Even considering my contempt for the idea that SJ was ever a basketball powerhouse, consider how few players over the past 40 years - I can think of Ron Artest, Chris Mullin, David Russell, and Malik Sealy - have had that combination of wisdom and skill. We've had just as many heralded HS players who did not pan out, either as freshmen or ever - Felipe Lopez, Zendon Hamilton, Omar Cook, Wayne McKoy, Shelton Jones, its a long list. The ones that did were NBA ready coming out of HS. If their rankings are any indication none of these kids are Carmello Anthony or John Wall, who are the sort of player that lead collegiate teams to top 10 rankings.
Consider a hypothetical game between a good mid major, say Butler or Gonzaga, and a team of high school all stars. Who would you think would win? I'd take Butler every time. Well we don't have a team full of all stars, we have players who participated in some all star games, and they won't be playing mid majors, they'll be playing Syracuse and Uconn and Pitt, teams that comprise three or four elite recruiting classes, of the sort that we're so pleased by, except their kids have for years been lifting weights and playing in their systems and playing against similar elite teams in the most competitive conference in college BB. Being an athiest I expect our frosh to get their brains kicked in, and if not heaven will be all the sweeter.