Organizer 2019 seems to behave so that it recognizes faces in photos up until some point. After that it seems to be unable to combine even almost identical stacks of persons and new faces. The analyzing process has completed in a sense that there is no progress percentage at the bottom and process is not consuming cpu. If I assign a name to even one photo, it starts running again with high load. Yet after that all the new stacks seem to be one image at a time from folders not earlier indexed by face recognition. This all sounds like a bug, what do you think?
If the progress of face recognition is not showing in the status bar, you can determine whether it has completed by looking in the Face Analysis/json folder in your catalog folder. The number of .json files in that folder should closely approximate the number of files in your catalog. The modified date of the latest file in the folder will tell you when FR has been completed. Face recognition should only take place in the background when no other activity is taking place on your computer. So it is hard to say whether you are experiencing buggy behavior, without knowing more about your situation.
I don't know for sure, but when you name a person in a stack, further analysis takes place and the identified face will be compared with other similar faces. In the Named People tab, new faces should appear under the stack for that person and you will be asked to confirm whether the new faces are in fact the same person. (You will see a blue triangle next to those stacks where further identification may be available.)
Face recognition is by no means perfect, but it does get better with each version. So, what you are seeing is not IMO a bug, but is expected behavior, given the limitations of the program.