Interesting post DJ744.
I can't shed much light on their operation specifically, but sounds like they are having trouble balancing their runways.
While their default runway/STAR allocations may well follow your suggestion, they probably find themselves oversubsribed on one runway with arrivals from one direction only, while the other runway is undersubscribed.
I guess they could just keep it simple and let the delays build but are obviously trying to be dynamic with their options.
Am I correct in saying you can load an alternate and switch to that fairly quickly, but not to a third option or back to the first so easily?