You most certainly would not! My French is awful. It is a known fact in my house that when Dad says, "You know, the French call this . . ." you should immediately stop listening and assume he is lying.
I use the French name for the dish in this case to signify the style as opposed to the usual American lumpy mashed potatoes with less butter.
It comes from the former r/rance now [email protected] where English was a forbidden language and everything had to be translated to the stupidest version of French.