This may very well be due to the fact that the nature of the romance scenes are very different.
In Yen scenes, you really feel that She and Big G have a history. There's a familiarity. It shows in the way they talk to each other, in their facial expressions (mad props to CDPR for these by the way). It's an old love, unbridled. There's also Yen's character of course, she being very blunt and, supremely confident and, let's admit it, a bit self-centered.
Triss is another woman, with another kind of relationship with Big G, and both are fairly well (if not often) depicted. You can see the sexual tension from the very start, the way she looks at, talks to and position herself in regards to Geralt during the introduction scene in the King of Beggars and Granary scenes. Triss is more earnest, and not-so-secretly hopeful. But the operative word here is earnest.
Here, new topic that totally hasn't been discussed to death in the last 700 (!) pages !
Since what we do all wish for is some more dialog options aboard the SS "Eredin Sucks Flaccid Cocks", what topic should she and Geralt discuss ?
I'm thinking a general "How are things turning out for the mages in Kovir" where she tells you about how the other mages are doing and how they and the Koviri government are handling things, available even when she's not your love interest, and a more personal "Soo, about that house..."
After all, she's mentionned in the fountain scene that she would tell you more about it, but all I could make out was that there was going to be a