How to prevent Photos for Mac from Shortening the names to the First Name only

Occasionally you may notice, that Photos will not show the full name of a person but shortening it to the first name only, even if we are entering the full name when naming the face. This can be very embarrassing, if the person in question is a person, we are not on first-name terms with or if we are using the Photos Library for business purposes.

In Photos 6 on macOS Big Sur this is working:

Try to set a short name format in the Contacts > Preference > General. Photos 6 will use the short name format you defined there. After I changed the short name format to "Full Name" in Contacts, Photos stopped the habit of using "First Name" only for the Photos, where I had used the name from the Contacts Card.

On older system versions you could avoid to use the names suggested from the Contacts, but then Siri cannot show you the photos of your contacts.