I'd assume that the cars stack up, and then a following car skips a stop in order to re-distribute, like a bus or subway line. The an elevator is a more concentrated system with more easily collected data, so whatever algorithm is controlling it would more easily detect patterns. So the stacked cars might not skip, in the case of say, a horde of people heading from the ground-floor of a hotel to a keynote on the ballroom floor, but might skip in the case of an anomalous delay like someone with lots of packages.