Woah I'm so confused now, what is a multiple pronoun? How can you be a She/Her/They/Them? Isn't They/Them the gender neutral option, so without She or Him? Are we talking like if you are an Alien and you have a disguise who is a female using She/Her pronouns, but the Alien Sim is a male using He/Him? Or your Vampire form is masculine, so He/Him, but your regular form is wearing women's clothes and uses They/Them? This is intriguing, maybe the mermaid form is using They/Them and genderless, because technically it's a mermaid so who can say what is mermaid gender culture, but the human form you might want to be male or female... I just, wow, I don't know, that's an interesting question, I hope you get an answer.
At any rate, I am really hoping for total optional customization here so that you can just type in whatever you want, hopefully, and then get dialogue options for that, and otherwise I really hope the game goes back to assuming gender based on CAS and using standard English. I think they should make sure there is not a small letter cap for the customization.
I support them adding it, even if I don't use it. I think it's more important for trans players creating a self-Sim and having fun with the game. It's not really something I need, but maybe we will get some new art work like paintings or deco objects from a Trans artist during the update so that would be cool. I don't want Maxis to try and be a pronoun pioneer and attempt to make history, they already lost that crown to Animal Crossing, so they should just focus on fixing bugs, making new content and refreshing packs not spend millions of dollars researching global pronouns in hundreds of languages because our Sims speak Simlish.