I think you're there with the last bit of your comment. The goal isn't to only move once, the goal is to minimise stops and starts. If everyone does this is a self sorting system. If someone has the rule "try to only move forward once every x minutes (unless you are at the front or the queue overflows)" then the queue gets into a rhythm that works.

In a queue like this there is extra effort in picking up your bags and stopping so the worst case scenario is everyone moving exactly as space is available.