My favorite example of that “out of place” rule is the trays in the cafeteria. They’re washed in exactly the same way as the plates (stack 'em on a rack, run 'em through the machine, if you can still see stuff on 'em, run 'em through until you can’t), but most of the folks I eat with consider anything that contacts the tray unfit for human consumption.
In general, the only things on your floor that are a greater problem than your plate are things that you can see. If your floor is covered in cat fur or tracked-in mud, then it should be obvious.