I doubt it does mean he has more creative control. Of course we don't know how Blizzard specifically defines the roles, but lead game designer is generally as high as you can go on the pure design side. Game directors also have oversight on production, meaning the development process, worldwide support structures, QA, and so on.
Personally, I have strong negative feelings towards the current generation of WoW developers and leads, for several reasons. First, because the already glacially slow Blizzard development process has actually worsened. And second, because they don't value communicating with players. We used to get frequent back-and-forth direct conversations in the forums, now we get very infrequent @Warcraftdevs tweets and proclamations in forums. It's a very different style, and I believe the game is much worse for it.