I would argue that for the sake of the law, having a backup of cars behind an officer all doing the speed limit is a good thing. It's called the speed limit, not the speed range. As in, the maximum you're allowed to do on that road in perfect conditions. If we want to enforce the laws, having everyone follow a pace car going exactly the speed limit is a good thing.

Having an officer going 65 in a 55 just to relieve congestion means the law is irrelevant.