Her being involved in WW2 or being a member of the JSA hasn't been a big thing in even longer.
Not at the same time.
And there is a comic book precedent that there are TWO Etta candies(a white one and a black one)
More stories and good stories are not the same thing. And I have yet to see a good story about Diana and the JSA.There is a lot more room for stories to tell with Wonder Woman as well that you can’t tell without it