Yeah, this just did happen this way.
Again they didn't have to give him the extension a year early and could have had him play under the $425K tender in his 3rd season and then tendered him again the following year. But they did. And he didn't even make the Pro Bowl at RT in 2005.
As for what he demanded, I don't recall $13M, but I do recall him wanting to be paid more than Derrick Dockery, who was making $7M/year. Speaking of which, yes, Brandon must have thought himself such a great negotiator, giving Dockery that deal, when he'd never even made a Pro Bowl.
As for the Bills not willing to give him $10M/year, there is zero evidence for that. That was the market rate and Ralph had made other great Bills players the highest-paid in the past. He just got pissed that he didn't get it when he demanded it and made the decision to leave, ultimately ending up making $10M/year in 2009, which is when the Bills wanted him to wait until anyway.