Here's the thing. I'm not saying creators can't do whatever they want, I'm saying that they must have an understanding of their own product and genre, and build elements upon it that belong to the world they've constructed, otherwise it will collapse on itself. The consequences of adding elements to your creation that feel out of place, or feel like they belong to an entirely different world/genre, is that the consumers will be confused as to what exactly it is they're playing/watching/reading, and the experience will probably be overall less enjoyable. Let's take Twilight, as an example. Can you make it so the vampires in your novel sparkle in the sun? Of course you can. Will some people like that? Of course some will. Was it then positively received? Nope. Not at all. Because some of the decisions they took for their story just didn't work.
Tl;dr: Being able to do whatever you want doesn't mean everything you do will work.
That being said, this is just a general opinion. When it comes to zombies being able to dig, I've got no problem with that. It doesn't feel out of place, and it fixes issues like players hiding away from hordes inside a 2x1 hole in the ground.