Do sims behave differently after the gender preference update?

I don't think woohoo partners is an autonomous option. If you initiate the conversation you can have woohoo without romance but it shouldn't happen on its own as far as I understand.
I think the Sims start out with no gender preference for romance but open to exploring so that they will respond to whoever you have flirt with them and develop preferences from there. They are just set to woohoo with anyone so that when you get the romance bar high enough they don't reject you based on gender.