Elements Organiser XMP Schema Missing

Following face recognition I use the 'Save Metadata to File' but sometimes Organiser writes the persons name in the People Tag and other times as a Photo Tag. Inspecting each file in Photo Elements I have noticed that the Microsoft XMP schema is present in the files where People Tag is used and is not present in the files where the more general Photo Tag has been used. Organiser seems to add the Microsoft XMP schema to some photos but not others.  The schema is not present in either file prior to importing into Organiser so Organiser is writing this information itself and sometimes not. 

I have tried exporting photos to new files but this doesn't make any difference.  What I want is to have the Microsoft XMP schema present in each file but I can not find anyway to achieve this.  Any suggestions?

and not present....