I have not been trying to excuse the way the People album is working now, but trying to explain, what is Apple trying to offer now. I do not like it either, because it is cluttering up my photos with unnamed faces.
Did you ever use the People album on Sierra, when we still could reject unnamed faces? This has been very buggy. The unnamed Faces album has been a mess of white thumbnails. I suspect the current way - forbidding the delete recognized faces is a bug fix, and it also helps with the scene recognition and the syncing of named faces with iCloud Photos.
You may want to send feedback to Apple with a feature request: Feedback - Photos - Apple
We need to be able to search for unnamed faces and to be able to get rid of unimportant, automatically detected faces, that are obscuring the faces tables of the people we want to name.