I beg to disagree, maybe we can debate on the "open world" definition, yet if you started as a lvl 1 dwarf, you could drag your ass up to Stormwind, because no frontier in the world forbade it. You could tried to get a kill on Sylvanas with your lame level 1 or explore STV. The world had no frontier hence the term "open world". You can farm/craft/explore/quest/pvp in no particular environnement deticated to such activities.