This is not true. Look into Zigbee binding, it works when the coordinator is offline. I'm using that as a backup solution in my house. All lights are zigbee, p

This is not true. Look into Zigbee binding, it works when the coordinator is offline. I'm using that as a backup solution in my house. All lights are zigbee, permanently powered, normally most are controlled automatically by presence sensors. But I have a couple of Zigbee remotes in a box that are bound directly to the lights to use in case my home automation system is down.