Not gonna respond to everything in your post, sorry, but this stuck out.
It seems that your stance in the above quote is mostly relevant to you (considering you seem pretty adamant about this stance), and not the player-base as a whole (unsure if you were trying to imply so).
If you were going from a factual basis, then yes, you'd be correct (as interactions with PC-centered NPCs puts no onus on the PC to be monogamous themselves), but it's a fantasy porn game setting -- a factual basis doesn't appear to be particularly relevant in that regard.
I'd argue that at least some (if not the majority, imo) of the player-base would quantify relationships with PC-centered NPCs as monogamous / monogamy (seeing as it's a porn game, expecting complete monogamy from the Player / PC is not a feasible criticism imo -- the NPC being monogamous to the PC is good enough for most), especially when that's intrinsic to the NPC, such as Brienne. Sure, it makes her characterization rather one-dimensional in the interim, but changing her characterization to something it wasn't initially (and wasn't hinted at initially) isn't going to make that better, it's only going to detract from what was already established.
That's largely why, at least in my opinion, some people had an issue with the way Azyrran's content has gone -- because it was initially presented in a different way to how it eventually ended up.
If reasoning is established initially to hint at something / a different possibility, then the end result can be argued to at least not be so jarring or questionable, because there was clearly some indication of such a possibility (such as Cait explicitly outlining relationships with her). Without it, it seems as though it's just done based on a whim, and thus leaves one with a lack of faith for such content moving forward (Ryn and Male PC's heir situation, Azyrran, Kiyoko's stance on the PC having no say in pretty much anything family related).
To end off, if I have to read the Codex for an explanation as to why a certain NPC is the way they are, and not find out through their actions and / or prior established lore (such as talk scenes with the NPC), then idk -- feels like I've wasted my time getting to that point with the NPC -- as the justification doesn't seem well established (imo).
Sorry, didn't intend for this post to get to this length lol.
