That's what I thought when I read the title.I'm guessing that since this class is designed for 3.5, you may not have been paying much attention to 4E. The Shadowfell is a new plane used heavily in 4E, being a dark reflection of the real world, filled with evil creatures and undead. Many people will look at the name of your product and think that it relates to that.
"Wizard of Shadowfell" reminds me of "Elminster of Shadowdale"