Truffle fries don't contain truffles. French fries don't come from france. I don't think the restaurant is to blame for our language. You want every restaurant to start calling them immitation truffle fries?

>French fries don't come from france.

According to Wikipedia, it's at least believed by some researchers that French fries originated in France.

Unless you mean "these specific fries don't come from France, any more than these specific fries contain truffles".

"Truffle flavoured fries"

Would be accurate and descriptive and makes them distinct from fries with actual truffle.

Gives you the same differentiation as whipped cream vs edible oil

Sure, why not.