Gateway means it is also a ZigBee hub, just like the SmartThings Hub.
For each ZigBee network there can only be one coordinator/hub. So this plug cannot be used a normal device. Software that links the entire Xiaomi / Aqara air conditioning gateway Zigbee network with it’s own devices to the SmartThings Hub would be needed.
There is already an integration for the normal Xiaomi / Aqara gateway. You should ask about Xiaomi / Aqara air conditioning gateway integration on this thread: