I just received my US version of the MSS315. There must be some FW version variation depending on the region? It came out of the box on 9.5.30 and I updated to 9.5.31 with no power stats capable on Homeassistant.
I emailed, and they responded they had just released 9.5.33. It must have been just a day or two ago because it wasn’t there when I received the plug initially.
Updated to 9.5.33 and now the power stats show up in Homeassistant.