According to this article, Scott refusing to sign the apology is the reason he was fired. How is that irrelevant?
That's their justification. I'm still skeptical. No offense, but an apology not signed by Cook isn't an Apple apology. Tim was gonna' sign it no matter what I believe.
It would have been signed by Tim Cook on behalf of everyone at Apple, but my guess is that Forstall wasn't on board, regardless of whether his name appeared on the public announcement or not.