Kotaku has a helpful look at the history behind this decision, which includes 6,000 Russian female soldiers during World War I. That means, no matter what any goofballs on Twitter say, this is actually historically accurate. The Women's Battalions will be playable as the Russian Scout class in the game.
The battalions were created following many petitions from women who campaigned to the government to join join regular military units, before they began protesting for women's battalions. Mostly because the Russian government thought it would make for great propaganda.
As you can see in the artwork above, the introduction of the Russian Scout class will also mark the debut of playable female soldiers in Battlefield 1 multiplayer. The addition of Russian female soldiers is another vital step in that direction. "New maps" and "new weapons" are included, as you'd imagine. The total estimated number of female solider in these battalions was approximately 5,000 by Fall 1917, but only two units were deployed to the front while the others served elsewhere.
We'll be at E3 2017, and will hopefully get a chance to check out the new Battlefield 1 expansion ahead of release. Watch this space for more.