I finally studied the Help PDF about the Trigger tab > 'Continuous AI analysis' feature. **
It's targeted at users who want to not consider static objects when analyzing a frame. Ken also notes that it's also a very powerful feature that is able to detect both abandoned or missing objects, along with simple object presence without relying on motion detection.
By default it checks every 120 seconds. Or every 20 seconds if objects are detected to have moved. So I doubt it's much of a resource hog.
For testing, I've enabled it for my driveway/street cameras.
I don't have a problem that I'm trying to solve. I'd be interested in hearing about specific use cases for this feature, if anyone has one.
** BTW, locating the correct section of the PDF was a bit confusing at first because the 'Help' button on the dialog currently lands on the wrong chapter section. (in 5.9.34 anyway; I've emailed Ken).