My real question is how changing boarding order affects the volume of overhead bins used. They kept emphasising that in the article, but I don't know what space

My real question is how changing boarding order affects the volume of overhead bins used. They kept emphasising that in the article, but I don't know what spacetime warping they are using. It could conceivably affect the way people stuff things into the overhead bins, so that baggage fits better, in some unconscious way.