Earlier quoted context omitted.
That just means someone in charge made a bad choice during planning and either no dev or designer ever dared to speak up against it or many of them supported said bad choice.
Why is it a bad choice? A game set in middle age Europe has no more reason to foresee needing the ability to mod gay marriage into it than accommodating modding cell phones into it. It's not an insignificant amount for work just to include an anachronism.
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.