Sensor Question: Occupancy Sensors Different Than Alarm Pirs?

In lighting system designs, Occupancy Sensors are used to automatically turn on/off lights based on movement in the room. They typically are mounted into light switches or look something like this:

I do not know much about these sensors. Can someone shed light on how they differ from an intrusion alarm PIR?

Occupancy sensors are generally more sensitive and meant to detect even miniscule movement. If you increased sensitivity on a motion detector to their levels, your false alarms would be huge. But the worst that happens when an occupancy sensor has a false positive is the lights go on for a bit.

On the flip side, if an occupancy sensor is poorly installed or too insensitive, it could fail to trip lights or turn them off on an occupant (had this happen), which can lead to trips and falls as the user fumbles for the lights (not gonna lie, had that happen, too).

So in general it sounds like not a lot of difference other than sensitivity settings.......