What Criteria is used to sort the outliner when "Sort Alphabetically" is off? The order definitely changes when I toggle that setting, but I can't tell what the order is changing to.
For the default All Scenes filter and excluding remapping users, it becomes sorted top-down by last added. This is somewhat obvious if you disable the option and just add objects to the scene. No object type takes precedence. To make sure, also checked the source and it seems to do just that.