The optional porn stuff is in game. Yet it doesn't affect the ending of the game in any way, so it doesn't matter. Tav and SH are still going to live on a farm. And no where in the ending does it even hint there's others included in their relationship. That is the canon ending. Are you arguing that isn't how the ending goes?
You do realize that just because people are open or poly, that does not necessarily mean they always have multiple partners at once, right? Especially in the case of a person like Shadowheart, whose boundaries include being each other's primary partners. Being open/poly doesn't just stop being true of the person when secondary partners for whatever reason exit the relationship or don't work out.
Your read that she's monogamous is true of your experience with the game and your ending(s). It is not necessarily true for others who chose to pursue the relationship opening up. As I've said to you in the past, your idea of what counts or not "because it's optional" or "because I don't consider it canon" is totally immaterial to how other people interpret the character development because they are not you and do not necessarily share your content filters. You need to at least accept that much because right now all you're doing is projecting that anyone who thinks otherwise is objectively wrong for how they've interpreted it.
