It's at least as real as Horford to Boston, right?
Not really. Atlanta declined to offer Horford the max (or the years), I think, and he felt spurned. Not saying he would have stayed, but that was probably the nail in the coffin.
There was one point where Horford wasn't content playing next to Dwight Howard. And then there's that other point where Hawks offered "close to" max money but Horford says "screw you I'm going to Boston for the max"...somewhere along those lines.