I had the same issue with ZHA + Conbee USB Stick and found a workaround by the hint of ZHA - Use Philips Hue SML001 as Occupancy Sensor for light control. I set o_to_u_delay to 5 seconds and then occupancy started reacting very quickly.
See screenshot: Imgur: The magic of the Internet
But now, motion detection doesn’t work at all. For now, I built my automation over occupancy but hopefully I can figure out how to use motion sensor entity properly. (I’m not sure difference between motion and occupancy for this device though)
See screenshot: https://imgur.com/ruyKSth
(Sorry, I couldn’t embed images since this is my first message here)