Having one all black final 3 in 39 seasons is pretty amazing.
Assuming each season has 20 players and 5 of them are black (they often have 3 or 4), and the final 3 are completely random. The probability of an all black final 3 is 0.0087 ( 1 in 114 seasons).
Also assuming that 50% of the players are women, we will have all women final 3 in about once in 10 seasons. I think it happened three times (16,24,29) so not very different from the expected value. Now we have 6 females and 3 males left, there is 24% chance we will have all-female final 3 this season.
Interestingly, there has only been one all-male final 3.