No French Allowed! (Dressing That Is)

Somewhat recently I visited my somewhat local Olive Garden. I hadn't been to an Italian restaurant in some time but I was talked into it by a group of friends who insisted it would be so great. So anyways, upon being seated we did the usual, ordered drinks, then spent time pondering what we would order before the waitress returned. Upon her return my three friends ordered ahead of me. While being the last one to order I was asked what kind of dressing for my salad. I responded "french" thinking nothing of this, and nothing else was asked. Now comes my confusion, upon receiving my salad, I did not receive any french dressing. Not a big deal I thought, I will just remind the waitress. At this point my friends along with the waitress began to laugh, thinking I was joking or something, my confusion continued. My friend further informed me that you cannot get french dressing at an Italian restaurant. I was completely unaware of this, has anyone else heard of this insane rule? I would be delighted to hear if I am the only one who spent 30 years of his life completely oblivious to this little law cuisine. Can I have Swedish meatballs at an American cafe? Can i have french toast in Mexico? Can I have American fries in Europe? Please someone
help me!