Going by the packaging alone, one would certainly get this impression. Upon closer inspection of the controller itself, this impression would disappear much like, well, an Xbox 360 guide button on a Wii peripheral.
Thankfully for Activision, the mistake is only a point on a bulleted list and the accompanying image of the guitar is correct. I've blown up the photo our tipster sent in and added some sharpening so it's more visible. Shame, I got a little excited by the idea of turning on my Xbox 360 with a Wii guitar.