It has never been in the NADAC rulebook that tunnels had to be bagged on the ends only. Ever.
It was just how things were done, but never a rule. We started to let our judges know they could start bagging them across the entire length of the tunnel through this past year.
It doesn't require a formal announcement because it's not a rule change, heck it's not even a rule update. It's just updating a preference.
As for the safety concerns. I can speak from experience that having the tunnel move is a larger issue then it not moving. Hyper extending joints, slipping and then falling on shoulders and heads. We have WAY fewer crashes with the tunnels bagged all the way through.
As for the dogs who hit them so hard they are hurting themselves, they are going to hurt themselves no matter what the tunnel is bagged like. If there is absolutely zero self preservation happening then it's the handlers job to provide that. If that can't happen then I would hope that team would maybe go back to training to get the dog to protect themselves a bit more.