This isn't about weird design decisions, the game uses an enhanced version of a very shitty game engine. (Ever heard the saying 'polish a piece of **** and it's still a ****?') There are instances where they tried to work around how shitty it was, meaning they knew about it yet probably couldn't do anything about it. Windhelm just so happens to be located on one of these faults, having designed the rest of the game around that area being where Windhelm was planned to be, it was already too late. Now you may ask, why not just fix it instead? Well my friend, you don't know Bethesda :P