Have seen this posted a bit (the writers haven't produced any twists since passing the books) and it makes no sense to me at all. Seeing as its an adaption of source material, isn't every major twist that happens in the show lifted straight from the books? Including from books that haven't been written/released yet? GRRM gave the show runners the low down on the major plot points and how things pan out - kinda makes it hard to infuse anything meaningful, shocking and plot-related that isn't in the books.
I'd say of course there have been twists since passing the books -
Bomberboyokay 's example of an undead dragon for example. I'd also say that it happened in the show because they were told by GRRM it will be in the books.