I'm not sure what I said that would imply that, but Xiaomi devices are (in this respect) like most other Zigbee devices: battery-powered devices are end-devices (not repeaters), and mains-powered devices (there aren't very many of these...) are routers (also called "repeaters"). So the answer depends on your device, but I think the vast majority of people here use mostly the battery-powered sensors, which are not repeaters.
What I was talking about was another issue: most "regular" Zigbee repeaters do not repeat well for Xiaomi devices, which can cause problems with the Xiaomi devices dropping off your network. These issues are well documented in this thread: Xiaomi & Aqara Devices - Pairing & Keeping them connected
