maybe thats not textured by Ubi. They might have purchased the 3d human model online (and yes it come textured with vagina) , model clothes on it, rig and then animate it.
As to why will that come texture with vagina, well that same 3d model can also be purchased by medical, science, art institutions etc for human anatomy studies and other uses.
And yes its a common practice in the game industry. Nearly every AAA studios does that.
Lol then why did they slap some crotchless panties on her?