I contrast that with my experience in Spain: Several meters before the machines, there is a large amount of unoccupied, huge tables with containers stacked everywhere, so everybody can get undressed and pack their stuff into the container trays at their pace of choice. Staff assists and tells the rules to individuall travellers. Once you are done sorting your stuff into the containers, taking off your belt etc - only THEN you take the containers towards the x-ray conveyor line. So there is hardly any blocking the line. Instead of a container-return system, a single human stacks the containers past the scan and returns them to the beginning. This is so much more effective.
Classic example of government run workflows: No one cares to optimize the workflow, and the one who would benefit from a speedup (the airport and the airlines) in terms of increased sales, have no say in the process.