Same problem using deconz usb ii. It takes 2-3 seconds after cabled sensors get motion. In this automation only the light is zigbee. I also have a zigbee switch connected to this very same light. Pressing it causes 1-2 seconds for light reaction.
Using hassio on ubuntu intel nuc i7 with deconz usb ii.
EDIT: could it be about the default transition on/off and this light is not supporting it? At least i know my light and sonoff zigbee switch doesn’t support it.
Switching off from within HA seitches the light off instantly, however switching on takes 2 seconds.
Tried the same with gledopto zigbee led driver connected to hue lightstrip, on and off are instant both with transition effects.