Baseball Reference uses 3000 plate appearances for their batting rate stats. Josh Gibson had(has?) 2526 PA so they don’t have him as the BA, OBP, or SLG leader. They are, however, counting the stats of the Negro League players. Oscar Charleston is 2nd in BA at .365.
So does this add stats to players like Jackie Robinson?
Yes, but in most cases, not much, relative to their AL and NL numbers. Part is that some of them only played a few years in the Negro Leagues, and part is that the number of verified games per season is much less than was played in MLB in that era.
Looking at Baseball Reference, which has been including verified Negro League stats for several years:
- Jackie Robinson now gets credit for 34 games, and 147 plate appearances, for the Kansas City Monarchs in 1945
- Larry Doby now gets credit for 141 games, and 618 plate appearances, for the Newark Eagles in 1942-46
- Roy Campanella now gets credit for 234 games, and 911 plate appearances, across two Negro League teams from 1937-45 (he started playing for the Washington Elite Giants at age 15!)
- Willie Mays now gets credit for 13 games and 48 plate appearances for the Birmingham Black Barons in 1948
Because of this, I’d assumed the stats were all merged years ago.