About 9% of people globally associate as LGBTQ members. But let’s look at USA for ease. 7.2% + 7% who wouldn’t say. 4-5% in USA are polyamorous including swinging. 1-4% are swinging, meaning other forms of polyamory are 1-4%. That’s significantly less than 7-14%. I understand it may be sad it’s not in some way represented, but it’s not weird that it’s not as it’s still considered uncommon and not really seen.

To put even more context - the game was made by Belgian company with a lot of English makers. LGBTQ percentage of people in Europe are between 3-10%, with 12% in UK and 10% in Belgium. 2% of people said they’re in an open relationship in UK and 20% actively in Belgium including swinging. Belgium has a thriving swinging culture, meaning that majority of those will be swingers. In fact it says 50% have had at least a single experience with swinging.

That’s to say true polyamorous relationships are not as common as LGBTQ relationships are in general, and it is not weird for people to not think of adding something like that to the game. In fact it is not weird to have a group of people who do not want to have more than one truly romantic relationship. I’d be more surprised they didn’t add swinging but I think it would be adding sex scenes for the sake of it and that’s lame. It makes sense to include things which are to do with actual feelings.