I'm not sure if primitive is quite the word I would use, however, I feel there's certainly more of an explicit ageless-ness to the character's demeanor with Frank: he's just a monster who loves his cookies (and to eat in general). Given the segments we've had in recent years, it's easy to imagine Frank's Cookie in Crumby Pictures, since those are far more parodic in nature with the education being more of an undertone; with Smart Cookies and Monster Foodies, where the education is more forefront, and Cookie has to learn about things, it's harder to imagine Frank's Cookie feeling organic in those environment, as opposed to David's.
Even in that Siri commercial, I feel like if it was Frank's Cookie, he would be going ballistic having to wait for the cookies to bake, and just start ripping up the whole kitchen, and shoving almost everything into his mouth. Instead, Cookie's playing with utensils, playing puppets with his oven mits, playing with the oven light - all very much childlike amusements.