I learned a little french in HS-- and i remember clearly, some words, like oui, to be said properly used different muscles than normally used in english.. Our french teacher would come down the rows, and gently poke our cheeks.. if we didn't winch in pain, (from sore muscles!) she would say-- you need more practice!
as faldage said.. different facial muscles are used, and this must effect wrinkles (or lack of them) and all sorts of other subtle effects.