The most likely explanation for the behavior is that creating multiple admin users on a secondary partition is such a niche use case that Apple simply didn't te

The most likely explanation for the behavior is that creating multiple admin users on a secondary partition is such a niche use case that Apple simply didn't test and/or consider it. This is a bug, report it and it will be fixed eventually. Most of the reactions here are overblown to a worrying degree. Surely an average HN consumer should have more common sense than that.