Catalog filter shows a count for these people.
Select this photo, Use : Metadata > Clean > XMP
use : View > Update catalog from files
 In catalog filter, the count stays at same value for these people. Selecting a people shows the photo, but there are no more xmp data and face tags.
  In catalog filter, the count stays at same value for these people. Selecting a people shows the photo, but there are no more xmp data and face tags.

 Thanks to your detailed description I can reproduce
  Thanks to your detailed description I can reproduce