Color. One of the more prolific posters on this board said the reason that WalMart took on OWOO is because they, OWOO, are a minority group. I believe this falls under the affirmative action umbrella. The poster did not say which minority group tho.
2900 is not all Walmart stores as there are more than 5000 stores. I do not see a skipped step, in fact only a couple or few of the doll versions are in the stores. This seems like a soft launch to me, Lena seems to be a common one in the posts. I seen 1 store with only Lena, yet one of my stores had shelf space for 3 which I seen 2 stocked. I believe this is far from a full out launch of everything OWOO.