I bought the UK H2 Wall Sockets because they support Matter and because I actually want to manage my power (Via Home Assistant). This came in in V1.3 of Matter.
The socket natively supports it, but doe snot differentiate to the socket. So, I added the socket via Zigbee (Which shows teh power on each socket) to an M3 hub and then used Matter to share to Home Assistant… but I do not see any power at all.
This leads me to suspect that the M3 is using an earlier version of Matter.