Weird. I'd wager a guess that he's not that in touch with his feelings, because the first sex he has with someone being grief sex doesn't seem like the most auspicious way to start. Either that or he had some idea and did it anyways, which shows some lack of concern. Either way he seems too fickle to be very interesting. I mean, yes, feelings do fluctuate, I could personally write an essay on that... but come on.
I do know some people that kind of remind me of that. They can get themselves so excited about the idea of something, that they can begin to believe their own contorted version of the truth. This makes it hard to ever know if they are 'lying', so it undermines all the confidence you might hold them in, as you just begin to see almost everything about them as somewhat dubious. But at the same time you can't entirely blame them, because they seem just as subject to their own deluded perceptions of reality. You can't really hate them, but they're entirely unmanageable. I think they're best left to their own devices, if they ever come to their senses it will probably be alone, because if you convince them they might just want to begin believing in a beautiful and partial truth again, and string you along on the way. So all of those things considered it's probably best to just avoid people like that.