You closed a thread on his 'word' saying that he is an expert, but he is 100% dead wrong, and really obviously talking out of his ass.
In the WoW 'world', by world I mean any possible technical view of the game, the first post is 100% correct, it is the reason you could use the ship/fear exploit to get to outlands a long, long time ago... it is because all of the zones actually float in a 3D space and while have seperate loading screens, are capable of being traversed through 'outer space' in the correct ways, such as the ship/fear exploit or dieing in certain places that send you to the wrong graveyards.
You might be tempted to go back to what that snake guy said, but don't, it is completely incorrect. It sounds like he knows what he is saying because that is how many games function, but that is NOT the case in world of warcraft.... he is making an assumption based on a false idea that WoW is the same as everything else.
You may say, well, what about loading screens? But the game only throws one up when you have moved to a different place and it detects that you have a lot of data needing to load. The game actually just 'teleports' you to the correct place and then the game client takes over and starts caching the area. Instances ARE their own servers, and thus actually are their own independant zones governed only by a loading screen, but anything on the main world server is traversable.
If you actually read this, thanks for your time.