I have got the same issue, however I would like to point out that the system is actually able to discriminate between "people" and "motion" as the app notification describes everytime the type of motion with a specific text (i.e. "there is a person at front of your door" rather than "there is motion at front of your door").
Therefore I would have expected that, when the "people on" features is switched on, the app would have muted any motion which is not generated by people whilst communicating instead only those notification which are relevant to people?
The app is actually able to make a distinction by clearly showing it, hence not sure why then it sends notifications for every event, regardless of what it is?
I'm having this same problem, however my "people only mode" worked GREAT for months, and now all of a sudden, I get a "Person detected" notification with any little bit of movement, person or not.
Just bought 2 outdoor wired cams and 2 indoor wired cams and I'm having an issue with People Only Mode as well. My wired outdoor stick up cams are alerting me about my dog in the backyard and a cat in my driveway, but when I leave for work and walk in front of the same camera that alerted about the cat.. nothing.