Slight correction, he was the first black starting QB in the AFL. When Briscoe played QB, the merger had not happened yet. An NFL starting black QB would not happen until after the merger.
Correction to the correction, the merger actually occurred in 1966, following which the AFL and NFL started playing against each other in Super Bowls. Briscoe started in 1968. So to say he wasn't the first NFL black starting QB is like saying the first four Super Bowls played are not part of the current NFL record books because they were played against said AFL teams. However, I get your point that it was not until 1970 that the two leagues integrated their schedules and adopted the "NFL" name as the merged name.