Right, what Tarlonniel said, altho chastity isn't required as part of the vows regardless. He says that some folks choose to take that extra step to show their devotion. But he hasn't. Still folks can continue to headcanon what they like (and Brianne has said explicitly that she left his past up to us...).
But... for exactly this reason, they wouldn't call him chaste later in the game.
I'm sure the line from Cole was just something random, never to be explained and therefore open for interpretation.
A lot of people forget they're not the same thing. Chaste also doesn't mean virgin, even if that is a synonym, people can be real sleep arounds and then have a huge change of heart for some reason or another and decide to go a more chaste direction.
Going by previous games (all) romances the very first time the PC sleeps with LI is when it's cutscened, which Cullen's happens after he's asked Inquisitor for a permanent relationship. This can still fit a varied chaste description.
Thank you, that's a point that's often forgotten. Even celibate doesn't mean virgin. If that comment was meant for Cullen (which it might or might not be, very few things from Cole are easily interpretable without context) it still doesn't say when he decided to be chaste. I admit, I place no religious values connected to either state; my standard is that people should never do anything which makes them uncomfortable or that they don't really want to do.
I think they intentionally left the first time (and other things) a lot more open to interpretation this time, actually. That's particularly the case with Solas and Josephine which in either case someone could easily chose to play their IQ as never having sex. Not so much with IB, Dorian, Sera, and Cassandra when it's pretty clear when the first time is. But Cullen and Blackwall, I think, both leave some room for interpretation on when their first time is. The common interpretation is that their first night was when there's a morning after scene that leaves no question. But I think there's plenty of room for someone to headcannon it starting any time between the first kiss and that. I've always felt Cullen was asking if the IQ wanted a long-term committed relationship, not that he was asking if the IQ wanted to start a physical relationship. Those things could go hand in hand, but they don't necessarily, and in fact the Dalish can ask if this is just a fling or is it serious which definitely leaves open an interpretation of more going on than a few kisses on the battlements. His writer made it pretty clear they intentionally left these things vague so people could headcannon it into the relationship they wanted. Those details have no story relevance for him, so why not (clearly what matters to him most is the commitment)? I love the fact that people can chose whether a romance with a couple of the LIs is sexual or non-sexual, and that others can chose the pace of the physical relationship in others, and there's no one right answer. After all, if I have a relationship with K, then somehow roll back time and have a relationship with S, it isn't going to be the same relationship, and all of our IQs are individuals, even if it's the same Cullen.