@chris I think using listExtendQuery() might potentially conflict with sortable columns if you have them enabled. Since the query ordering would always be applied, it could alter user-initiated column sorting.
Maybe you could consider checking if there’s any active user sorting before applying your default multi-column sort?
If you’re looking for examples of how to detect active sorts/filters in lists, you might find the List Saver plugin by SixGweb helpful. It’s mainly for saving list preferences, but I believe it has some interesting code showing how to access the current list state.