I hadn't heard this particular version of it tho, and honestly, it's far creepier in my opinion than the other one at the War Table. Whether Cullen was in love with the mage warden or just a crush or infatuation or whatever, the fact that he's hounding Leliana to talk about her, to the point where she gets snippy about it, seems . . . odd. Esp if it's for an US warden, it seems rather callous of him. Another OOC Cullen moment? :/
You know, I've thought about this for a long time, since the first time these audio clips came up and we had those kerkuffles in the thread about whether they were creepy/obssessive/romantic, and I think now I get the point Brianne was making then - he's curious.
Under the very, very specific circumstances you need to meta-engineer to get this banter, I actually don't think it's too out of character for the person Cullen is in that world state. The mage Warden is dead, so Cullen is not only dealing with unresolved feelings about her, but also double the survivor's guilt - and I don't even mean romantic feelings; regardless of how she felt about him or how he still feels or not about her ten years later, she saved his life at the tower and he never got to thank her for it, or apologize for the things he said, or settle any open score between them, and he'll never have the opportuniy to do any of that now.
Then, of course, the mage Warden romanced Leliana in the brief time between the last time Cullen saw her and her death at the end of the Blight, and in the weirdest turn of fate, this random person his old crush found in some tavern and fell in love with and in whose arms she died, somehow ended up coming to work closely with him a decade later. It's weird, you know. This woman who knew the mage Warden more intimately than anyone else in the world, who knew her infinitely better than Cullen's carefully distant contact with her could ever have afforded, is standing right there, with this whole history of love and loss in her past that involves someone Cullen once knew and liked, even if only superficially compared to the relationship the Warden ended up building with Leliana over some short time later.
And finally, Cullen is not in a relationship with the Inquisitor, so all the time he would otherwise spend thinking about the Inquisitor, being with her, building a strong relationship, learning to leave his past behind (not just romantic, I mean all of it) and live in the present with someone he can build a new life with, etc; is time that Cullen has to nurture old ghosts instead, gnaw on those old guilts, that small paranoid voice that eats you up inside saying you should have said this, should have done that. Even if he's friends with the Inquisitor, it's not the same. Being in love with Inky would consume his every thought (which is why the banter won't trigger if he's being romanced, he's not letting any of that weight on him anymore); but being alone means he has all this time to worry over the same thoughts - she's dead, Leliana knew her so deeply, I barely even knew her, I wonder what she was really like outside the Circle, I wonder what she was like when she could freely love someone, I wonder if she ever forgave me, I wonder if she even cared, and now she's dead so it doesn't even matter, etc. He's curious, and Leliana is the only channel he has to approach these questions. Asking Morrigan anything is not an option, Loghain/Alistair were just passive audience, Dagna only met her once... the only person who could hold the answers he's looking for is Leliana herself, who, of course, is the one person he should leave alone about these things.
So yeah, in the end I still think it's creepy. It's creepy as hell, the way he's prodding Leliana with intimate, intrusive questions about her dead girlfriend. But in retrospect, it also totally makes sense? Because Cullen is a mess of unresolved tensions and traumas in this world state, rekindled by this bad karma joke of having to work with Leliana now, of all people, and he doesn't even have the emotionally stabilizing factor of a more adult relationship to help him let go of things that don't matter anymore. It's super obssessive of him and uncomfortable to hear for us, but it does make sense for the Cullen that has to live in that specific emotional wreck of a world state. He's overthinking everything, and curiosity gets the better of him.