Pretty sure GH3 hit stores near a month ago, which means the demo guitars were out there long before that. They had enough time to know they weren't going to work to at the LEAST put out a statement before the game was released so us poor people that forked out $60 for the standalone disc wouldn't be hosed.
What? Do you really think RedOctane thought, "Hmm, those Harmonix guys are creating a game similar to ours that everyone is viewing as direct competition to our franchise. Let's send them over one of our demo guitars so they can try it out on their own game!"
Please. Harmonix had to get a hold of the Les Paul the same way everyone else did. Best Buy.