Sims from China do eat everything with chopsticks. It's a hidden trait called "Asian Culture."
Exactly like I thought. Because the Chinese sim who joined the family did eat everything with chopsticks, from cookies to Angle Food Cake.
Probably explains why they will do 5 hours at least to eat soap with chopsticks, but that's another story.
I've heard that getting this hidden trait is only 50%.
And if sims do, do they need to have all the benefits from the Asian Culture at once? Because my sim who was partly French only inherated the ability to go to French cheaper ($800,- simdollars or so?), I didn't saw him doing the special double kiss.