I think it is simply an attempt to reflect modern society. Does anyone remember the Justice Alliance of America from Earth-D? It was a one-off comic pubished in 1999, although it was a story based during the 1985 crisis.
I've heard that it reflected what some of the DC writers hoped would happen after the 1985 crisis - that the Justice League would be more ethnically diverse. It didn't happen ofcourse and the League remained pretty much 100% white apart from Martian Manhunter, who's green.
I think the DC writers are trying to hit thr ground running, this time, and make sure they expand the DC universe in a more human way. So not all the characters will be white and heterosexual. Good on them for that!