That hiding survivor was a good plot twist. I didn't see it coming. More intelligent zombies is nothing new, though. Depending on how the author wants to develop the story, it can be a necessity. If the author doesn't want to go for a basic survival story, like how to manage food, shelter, medicine, containment/infection preventation, and such, what I'd call passive threats, then the active threats are more important. That can be either other living humans or more dangerous zombies.