Just so you know, I'm not trying to change anyone's opinion on this matter. Everyone clearly feels fairly strongly about their stance and it is rare for an internet debate to change anyone's mind. This is just to discuss my thoughts on the matter and to offer a different viewpoint for anyone that may be on the fence.
First of all, I simply cannot agree that having passing sexual thoughts and occasionally feeling tempted amounts to NTR. If that was the case, then nearly everyone in a relationship is NTRing their significant other on a fairly regular basis. If I was out drinking with a female associate and thought to myself "damn she has some nice tits," and then immediately followed it up with "What hell am I thinking? I'm a happily married and don't need to let my mind wander down that path," no one in their right mind would accuse me of cheating.
Next, I don't see the game as trying to push you into NTR. In the next scene in Greyhide's arc a very similar senarior plays out between him and Rowan when they drink the same aphrodisiac spiked alcohol, you then have the choice between making out with Greyhide (leading to more), or to drunkenly gush about how good of a friend he is. But the game isn't trying to push you to be gay. It is jsut presenting you with that option if you are interested. If not that is fine too because the senario is written to account for that choice. In the next scene it is revealed that Jezera had secretly spiked Greyhide's liquor, hoping for some interesting results. This scene will play out a bit differently depending on if Alexia fooled around with Greyhide, whether Rowan did, wether they both did, or whether neither of them did.
I also don't agree that having a choice implies that the character really wanted to do a particular option. It is just a moment where the developer is asking either "what would you do in this situation," or "what do you think should happen next." And in the way it is presented, these are clearly intrusive thoughts and not normal for her. In fact, most often she is able to reject any advances quite firmly. In the prologue when Alexia has been captured for a while you are given the choice between "she warmed up to Andras" or "she remained cold and aloof" is doesn't make sense that she wants both considering that it is asking how she has react for the past several months, it is asking you what you version of Alexia is like. By the same token When Rowan agrees to serve the twins and he is ordered to service one of them sexually and you can choose which one you want, it isn't saying that Rowan wants to have sex with both of them equally, it is asking you who your Rowan is attracted to. By the same token when you are asked to make the choice between "ask to see Greyhide's dick" or "shake of the aphrodisiac" it is asking you what kind of woman your version of Alexia is. Is she the type to give in to her magically induced lust, or is she the type to resist and remain faithful to both her husband and her principles.
Finally, I find there is usually a pretty big double standard in these arguments. By the time you get to the Alexia/Greyhide scene, Rowan will likely have had dozens of encounters with women (and possibly men) trying to temp him, and he is usually presented with the same two choices, either give in to the temptation or to resist the temptation. But I never see anyone complain that Rowan is NTRing his wife regardless of whether or not he ever gives in.
All that said, while I still disagree with your stances, I understand that other people will also have those stances, So I will endever to take that in to consideration in the future when people ask about NTR in this game. I will let them know that both of the protagonist will have other characters try to temp them in various ways, and that sometimes they WILL be tempted. But that the ultimate decision as to whether or not they will act on those temptations is up to the player. So if you cannot stand the idea that your SO may find other people attractive, and may at least be tempted on occasion then this may not be the game for you.