It's interesting that the floating nut plate (Item 74) is shown in the EPC, but not in the exploded view in the Service Manual. A close look at the photos in the manual reveals the nut plate however.
The question here is whether the nut plates were lost during a previous service of the center bearing, or if the welded structure of the floor has rusted away to the extent that the pockets into which the nut plates are inserted no longer exist.