Welcome to the Wyze User Community Forum @lpapineau! 
The Detection Zone is based on one static Field of View Home Position. When you have objects or zones blocked out in that one Home Position Field of View, and then the cam actively moves during its Scanning cycle with the Scan feature enabled, you would have up to 4 waypoints all with a unique Field of View. The cam cannot create a unique detection zone for each Waypoint Field of View. Rather, it turns off the Detection Zone when Scan is enabled so that the one DZ set doesn’t interfere with detections in the other 3 waypoints or while scanning.
It is possible to do this. At least it is designed to do it that way. Turn off Scan, Turn off Track Motion, Turn Off Detection Zone. Set the home position of the cam by using the app to aim the cam. Turn on and set the Detection Zone restrictions. Turn on Track Motion.
The cam will pick up and follow any motion it sees in the Field. When motion stops, it should return to the Home Position and wait for the next motion event.
I say should because the cams have been having major issues remembering how to get back home. Wyze is working on it.