I don't see it as lying to say that your KD is your intimate partner.
There are two reasons to frame your relationship that way:
1. The clinics generally use stricter rules than the FDA requires. The FDA does not provide a definition for their term "sexually intimate partner." Medically, in terms of risks of STDs, a KD should be considered the same. So in my book, it's not lying when you are given a heterocentric lack of definition and apply it to your situation. I was upfront about most things - the cinic knew we had separate insurance, addresses, and telephone numbers. I actually didn't lie about anything, I just let them assume.
2. The insurance companies are discriminating against queers. Straight people do not have to prove they've been having unprotected intercourse. I know straight people who had birth control scripts, tried for 6 months post-BCP, didn't get preggers, lied to the insurance about trying for a year, and nobody ever checked her health records. If they had, obviously they would have seen a BCP script six months ago.
On the flip side, queers have to prove what they've been up to, and have to have licensed medical providers perform it.
Also, straights - one year of trying. Queers - 12 cycles of doctor assisted IUI. For those who aren't even ovulating, or who have longer cycles (common with annovulatory cycles), that takes longer than a year. Also, the cost, given that many of us are using donor sperm, plus the cost of the IUI, a typical cycle can easily cost $1,000. And that's unmedicated, unmonitored.
Last, the insurance company's rules are bogus. You shouldn't have to wait a year to have coverage when you have a pre-existing diagnosis.
So, back to the original question - how do you fight with your insurance about it?
You threaten to sue them. You find a lawyer, you point out that you know the law and the law does not require intercourse, and that their actions could be seen as discriminatory since they have different requirements and impacts on straights and queers.
NB: It is legal to discriminate in the US and in MA on the basis of marital status, so tread carefully there.
The insurance company does not want a lawsuit, because they would lose. various queer community legal services MIGHT be able to help you.
It's not easy. You have to fight. And you can't talk to the person who answers the phone, you have to get a claims supervisor, likely someone in their infertility working group who actually understands this stuff.