Considering how detailed he was 20 years later on some of the stuff, I doubt that. This guy got off on those memories. Plus he was caught because he couldn’t help himself and liked the attention years after his last killing.
I think some of these guys just don’t want the further trials and probably see no benefit to admitting anything more. Maybe that is where he is at. Or maybe he just wasn’t involved. Though the police should investigate it still of course.