I totally could have missed names, but what I did is pull up each national championship roster and comb through to see if any of those guys ever made any NBA roster.
In the case of Syracuse, it's a rare exception where there truly were only 2. UConn's team last year may be the next anomaly.
4.6 is slightly misleading b/c some players may have only played half a season, others flame out early, etc. But yes the average is 4.6 people that put on an NBA jersey at some point.
Pretty crazy when you consider others on those rosters also had overseas careers. Takes insane talent to win it all.