That said, the cuts they are making on the show seem like the smart thing to do.
My understanding is that books 4 and 5 occurred simultaneously in terms of chronology, with book 5 overtaking the events in book 4 (yeah, I admit the setup is weird and dumb). Book 6 will abandon that and just tell the story as it goes. It will not overlap the timeline of book 5.It's also a product of the terrible choice GRRM made to leave out a bunch of characters so that when the 6th book is released we'll be reading stuff that happened simultaneously with the events of book 5.
We've already been forced into an entire season without Bran and Hodor and Arya's storyline is way, way ahead of where it should be. If they keep her in the House of B&W we'll see very little of the show's best character this year.