Yeah- that is pretty much true.
There is a tiny bit of content that is somewhat like that though. It is just often really buried under conditionals and not very exhaustive.
You get can get a really sweet Rowan x Alexia scene at the end of the entire Liurial plot if you don't sleep with Liurial at all. Have a positive Relationship with Alexia and Alexia / Liurial became friends.
That is like 12 scenes for 1 though.
There are a few scenes here or there similar to that.
In example, you cannot get the Rowan X Alexia Catacombs scene if you sleep with either Twin more than once on Alexia. But again you're trading like 250 cgs for like 10

.
If you are looking at which kink is getting "rewarded" it is definitely not the faithful players. Presumably the content menu for faithful players should improve a bit as the game moves forward- but sadly most of the relationships (even the ones that can become wholesome) start with cheating, coercion rape, or drug rape.
Exceptions are:
Liurial x Rowan x Alexia
X'zaratl x Rowan x Alexia
You can start both of those without any cheating at all.
I'm interested to see if the Helenya plot-line Rework might allow for a non-cheating variant to throuple-hood. It depends largely on how(and how much) Winter touches up that initial Siege of Raeve Keep content.