Whilst I agree that it's essentially true that lesbians want women and not men, I actually know of quite a few trans guys who are in successful relationships with women who identify as lesbian. This might be because women (as a whole) are more open to dating people outside their usual self-identified sexuality. A part of me worries that there's an underlying hint of transphobia there (i.e. that some of them may think it's okay to date a trans guy because he's 'not really a guy') and I find that a bit unsettling. But I'm not here to police other people's relationships and if a couple has found a way to make it work, then who am I to judge?
In most cases I've encountered, the couple started out in a lesbian relationship before one decided to transition and their love for each other was strong enough for the relationship to continue through and after transition. So it can happen, but the lesbian dating pool is small enough as it is, so I'd imagine the number of lesbians within that pool who would be open to dating a guy would be even smaller. Perhaps it's a lesbian dating puddle.
But if you're looking for a brand-new person to date, you might encounter some negative reactions if you start looking for lesbians, because yes, they're on OKCupid because they're looking for women and some of them might not take kindly to being approached by men. For that exact reason, many of them will have their profiles set to not show straight people (mine certainly is, but that's a different story).
So why not try looking for bisexual women and straight women (i.e. women who already identify as being attracted to men)? For one thing, a lot of the bisexual women on there would love something other than the usual creepy guys whose opening gambit is 'fancy a threesome with my missus?'.
And another thing... I hate to say this, but many cis people think of 'trans person' as meaning 'trans woman'... or more accurately, they may think it means 'a man who wears women's clothing' and that might be why they ticked 'no' to that question: because they're specifically looking for a guy who presents full-time as a guy. But many of them are not even aware that trans guys exist and that some of us are straight, so it wouldn't have occurred to them that 'trans person' includes guys too. So of one if them seems otherwise promising apart from that one answer, why not message her anyway and see how it goes? A little education could go a long, long way - and you might find a diamond.
