PIR/Ultrasonic Sensors used in an Occupancy Sensor

I am confused about why the Occupancy Sensor Cluster (ClusterID 0x0406) lists PIR/Ultrasonic sensors as its optional OccupancySensorType attribute (AttributeID 0x0001)?

My understanding is that an Occupancy Sensor is suppose to sense if a room is occupied (ie - would detect a motionless human). A PIR/Ultrasonic sensor can only detects motion and therefore cannot detect the motionless human in the room. Therefore, I feel like a PIR/Ultrasonic sensor would be better fitted to be for the IAS Zone Cluster (ClusterID 0x0500) Motion Sensor.

What sort of answer do you expect? I don’t think anyone here was directly involved in the Zigbee cluster specification, so the only thing we can do is speculate.

Aqara motion sensors use both clusters.