I don't think this is as similar to.the Wii u as y'all are thinking.
The game pad for the Wii u was literally forced on us in alot of Wii u games. So much so that it had to be on even if you were using a pro controller or, in some cases you had to use it as the main controller period. And was integral to alot of the games on the Wii uand how you played. (Star fox zero.for example)
This just looks like a more.integrated ps4/psvita situation. Where, you have the option to take the game with you but never have it forced on you like with Wii u.