Do you mean Settings>General>Reset Suggested People & Pets ? I don't think it resets the People & Pets part of the database. And I Hate (capital H) the way many apps and Photos in particular often 'suggest' what I might like. So I'm not going near that.
However, I have solved the mystery of why three photos of my cat appear: he's climbing on my shelves, and among all the toy bears, electronic games, clocks, spare batteries and whatnot there's a tiny (5cm) bottle of sand which has my name written in a different colour sand inside. Astonishingly, Photos had picked up on this.
I also found a photo which wouldn't allow me to add a keyword. Putting the cursor in the appropriate place and typing did nothing. Just that one photo.
Anyhow, let's wait until it's completely finished indexing and see what happens.
Oh, one more question: if a face is marked as 'unnamed', is that Photos's final decision, or might it realise who the face is during later indexing? There are some 'unnamed' faces which are pretty similar to those it has correctly identified.