@ThreeLocusts
You ask why he would lie about being a woman. To get into your head would be my suggestion for an answer. He's trying a new tack. Keep your guard up.
This. Please see this for the enormous red flag it is, OP.
He knows you. He knows you’re bi and so feel part of the LGBTQ community. He knows you think it’s important to “believe trans people”. He knows this is the best way to get back into your head, to make you question your decisions, to weaken your boundaries.
And it’s working. Look how confused you are already, how willing you are to believe him and accept his preposterous “explanation” for the abuse.
This is him still abusing you. This is what abusers do. You have managed to escape his control and protect your DD from him; this is him responding and trying to reel you back in, by appealing to what he knows your beliefs and values to be. He’s playing you like a fiddle. He doesn’t want you to get away from him, he wants to keep exercising control over you, because that’s what abusers do.
I can only second the suggestion upthread to do the Freedom Programme. And the one to read Lundy Bancroft’s Why Does He Do That.
You have done so, so well to get away from this man and safeguard your DD; huge congratulations on that. Now you just have to recognise this for what it is and hold firm against this new attempt to abuse you. And be prepared for him to keep trying to get at you. If this plan doesn’t work, he’ll likely come up with another.
This is what abusers do.
Stay safe.