@kindleBunny: IIRC, the Collections view only ever showed Collections, then *unfiled* items. The sorting order was either by date or title, can't remember.
The other issue you mention leads me to believe 'by date', which is why it relies on a stable time keeping to work in a reliable manner

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EDIT: And the ScreenSavers mention confirms that, it also relies on a consistent time keeping to get the last opened book.