Do you mean the symbols next to "This is you"? I think you're misinterpreting them. That's the character's sexual orientation. It's always there, regardless of the character's marriage status. And gay or lesbian characters can and do marry people of the other sex even if that would not be what they want. The sexual orientation symbol doesn't change.
But it's not a good reason for why they are blocking all discussion about a mod that implements the feature in a buggy way.
What's an anachronism in a sea of many others, if you wish to have them in your personal save games. And if you don't, you stick to whatever is historically accurate.
Not having the foresight to be aware of this matter and the issues that come with it(going as far to be be especially exclusive) as a game studio in 2020 is what they should think about the next time they set out to make a game like this.
Maybe games just shouldn't be rushed out this much either.
Apparently one can marry a piece of furniture with the scripting language, so long as the sex be appropriate.