AF and KL want to operate with the same products (=classes) between AMS and CDG. So KL offers premium economy on AMS-CDG flights.
On flights between Amsterdam and Paris, Europe Business Class is divided in 2 zones. All middle seats are blocked in the front part of the cabin (C-Class ticket holders).
Whereas these seats may be occupied in the other zone (for premium economy tickets). Both zones offer Europe Business Class services.