I get that but I would like to have an answer on if they did sleep together or not... it can change some of the tenor about things. You get the sense from him about getting you into bed that you have but it could just be a quip comment about his intentions that he doesn't follow through on.
Then there is Sera's comment about her betting he screams out ELVEN GLORY when he does it with you that makes it seem like the two of you are sexually involved. No dialogue to refute that the two of you are sleeping together so..... could go either way I suppose.
From a save point on the final romance scene I went half a dozen different directions to see if it would turn out differently at all and it didn't turn out too differently though one caught me as significant. She shoves him and get angry and shouts at Solas telling him to tell her she was just a casual dalliance so she could move on. To me that highly suggests they were sleeping together... I don't think a kiss or three and a butt grab a "dalliance" make.
My first playthrough of DAO was a city elf and that story kicks of with an arranged marriage. We get to see a bit of a Dalish relationship in DAO as well with that hunter who hasn't quite made it yet and the girl he likes. Between the two of these I get that Elven culture, city or Dalish, is rather rigid with relationships. I don't think you are generally expected to bump uglies and play around until you finally decide to settle down. To my mind this means that if Lavellan and Solas were sexually involved it was a pretty big issue... likely for the both of them; a way bigger issue than just some making out. But I could be totally off base here.
Yeah. From what I gather, (and this is a lot of conjecture here) Zevren and Sera seem to be atypical elves in that regard. Both are shown as being comfortable with casual intimacy/sex. I think this could be connected to the fact that neither had strong ties to an Elven comunity. Both have jobs that discourage 'putting down roots' so to speak.
With Merril she's like 'hey let's move in together.' Dalish and city elf comunities (from the little we've seen) seem to have very structured courtship rituals.
So I think you may be on to something there. *shrug*