Just purchased Sonoff temperature/humidity sensors (SNZB-02D and SNZB-02P) to be used with Google Home to automate the HVAC. The default temperature in these sensors are Celsius, but you can change it to Fahrenheit in the setting, which I did, and it correctly shows °F in eWelink.
But when they’re integrated with Google Home, the temp reverts back to °C, even though the default temp in Google Home is Fahrenheit. I know this because it shows the thermometer in my HVAC as °F. So it’s not the fault of GH.
I also connected the devices to both Alexa and Samsung’s SmartThings. Alexa shows the temp in°F, while the SmartThings reports it in both °C and °F.
Hence, I’m of the opinion this is a bug in Sonoff. Even though it’s showing the correct format (°F) in eWelink, it’s obviously relaying it in default temp (°C) to other devices. Or maybe this has something to do with “country codes”, like Google Home thinks the device is located in China, where Sonoff is made?