Idk what you mean about things being unflirty. Laezel is the only one who's like "let's fuck NOW.". Shadowhearts scene is filled with tender moments and subtext, and Astarions scene has a TON of flirting. As for the foreplay, that scene is under construction. We'll have to see how it plays out in the final game
Personally, I think before the romance triggers for any character, or the start of it as I am assuming is the point of the party scene, you should have to trigger a couple "flirt" conversation options during gameplay. DA:O did that, and that game is probably a gold standard for me personally for companion progression. It is just jarring, not having any interest in other companions, then all of a sudden that night (maybe one of those damn tieflings dumped some spanish fly in the beer) every companion wants to jump you for bare minimal approval. Minimal meaning nothing more than story progression choices.
The scenes themselves, or what they have available are very well done. Nothing too saucy from what you can see in a rated R movie. I mean the Minthara one was great, the Shadow one was wholesome (which I think she is meant for the main female relationship storyline I am guessing) and the Astarion one I am sure got all those goth, vampire lovers full of joy. Lae'zel I haven't gotten to pop yet, though I saw it on YT and it was fitting for her character.
I am just glad that Larian has displayed some nerve to include a more adult scene in the game. I guess that is a perk to a European developer.