Bugliosi corrects Posner a few times in reclaiming history and calls him out by name. Not sure if there was a bit of needle between those two or if bugliosi was just simply trying to set the record straight on things.
Well, more than corrects him - he very strongly criticizes him. Not just in the book but in interviews too.
As to LN "lockstep" thinking: There's disagreement among the lone assassin believers on among other items: the timing of the first shot (and what happened to the bullet), whether Tague was hit by a piece of that shot or a piece of the skull after the third shot, the Odio incident, where the head shot entered JFK's skull (near the cowlick or lower down), and most important Oswald's motives. People like Max Holland say Oswald's act has to be placed in a Cold War perspective; that Oswald retaliated for JFK's anti-Castro policies. Others say he acted out of pure self interest, of a desire for notoriety and politics weren't involved.
Other than that (and I left some out) the "lockstep" characterization is spot on.