There is no way to reject the faces of strangers, statues, artwork, etc in any version of Photos since macOS 10.13 High Sierra. The earlier versions of Photos allowed us reject the false positives, but the more recent versions of Photos are keeping each and every detected face, even in crowds of people, because Photos needs them for the Artificial Intelligence to recognize the scene, if the photo is showing a concert or a sporting event or similar. At the time Apple removed the "All Faces" album, because we can no longer weed it out and searching unnamed faces there would be looking for a needle in a haystack.
When I am coming across a photo with faces I do not want or need to name, or photos with no people in them at all, I am tagging them with the keyword "Strangers", or "No_people", or "Artwork".
Then I add keyword rules to my smart album to suppress the false positives, as shown in this screenshot and combine the rules with "match All".
By the way, I am also naming the faces in paintings or of statues, when I want to remember who the person is. I am using the People and Pets album to add named tags to all kinds of things in a photo, where I need to add a marker that can be removed, to tag a constellation or a comet in a photo of the starry sky, or mark a part of a rock that looks like face. The faces circles are very convenient to add removable markers to a photo without spoiling the photo.
