This again?
It isn’t Black QBs — it is that no “running QB” has ever been in, much less won, a SB. And most Black QBs take off quickly.
Doug Williams was a pocket passer IIRC.
Joe Kapp was in superbowl IV. He sure wasn’t a passing quarterback...
He is the only quarterback to have played in the Superbowl, the Rose Bowl, and the Grey Cup.