I think they'll ignore intersex people the same way they have been, and how they ignore trans men when harping on about sports.

Focusing on an immutable sex is a core part of transphobia and their world view. By pretending science is broadly on their side they can recruit more people to their side. Look at how even "allies" often use agab language- the same way these fascists use biological sex. Lots of people focus entirely too much on how someone was born. That's what they mean by biological sex and I think that's easily digestible for a mainstream audience.

Half assed ally libs are learning how to bring up intersex conditions and push back against the idea that it’s an immutable binary.

They've been doing this for a long time, it doesn't do anything. Its off topic and a weak defense. Its easy to dismiss intersex people as a birth defect or whatever (not that it is- just that's the easily digestible view and an easy explanation).

Also, they benefit from not making it clear what they are getting at. Do any of their terms really say what they mean? Look at abortion, they aren't actually pro life, abortion isn't "murdering children", they call fetuses babies ffs. They are very willing to blatantly use the wrong terms for things if it sounds more convincing in an argument and biological sex is way more convincing for fence sitters then god given sex, same way calling a fetus a baby is more convincing.