Well, maybe it reads that way (that I'll never get what I want from this guy), but the conversation didn't feel that way at all.
What it seems like to me instead is that this couple are beginners. He (I'll call him Tim) said to his girlfriend (I'll call her Anna), "I want to have another partner who is a woman, not a man". She agreed, thinking he'd have a hard time finding a girlfriend and so she didn't really have to worry about it; and then bam, he found me very quickly. They didn't get around to doing the talking that they should have done, back when they should have done it. She preferred (and still prefers) to ignore this completely and not think about it. He hates to bring the subject up, because it just upsets her for no good reason, since there's nothing in it for her.
We are all the same age (mid-forties). And we are all pretty similar personalities; introverted, conflict-avoidant, polite. He actually thinks that Anna would feel less resistant if she met me, but she doesn't want to, and no-one is going to force her to.
He tells me that when it comes to my complaints about my needs not being met, that he never really took the time to think about my needs at all. He was just so excited that Anna consented to this, and so he jumped in blindly. We met, I agreed to go out with him, he took my agreement at face value, and now that I've told him "oops, no", that I don't like the terms, he is open to thinking about my terms, and to try get Anna to listen to them.
But of course, that's a challenge, because she's not interested in hearing about any of this. I'm his problem, not hers. And while Tim's motivated to keep me happy and keep me around, Anna couldn't give a flying f*ck.
So he has asked that I be a little tolerant, and let their talking catch up to my thinking, because they are new to this poly thing and don't yet know what they're doing.
I think that sounds sincere and honest, not hopeless.