It is a bit more nuanced than that, AFAIK they added female versions of a specific subset of human military, which for all this time were explicitly male with various lore reasons supporting that fact.
I’m not involved in the hobby myself but went on the occasional lore reading spree on the wikis, as s disclaimer. But I can understand that fans are upset about retcons such as this, where there wasn’t much ambiguity in the lore to squeeze the change in, making it a pretty hard lore break