Got this as part of AerisWeather (aka owners of pwsweather) update email:
If clicked, it redirects to this article (link). Based on this, and other info from integrations center (link), it seems official that while Gen 3 supports selecting individual weather station from WU network for rain data, WI+ itself runs off aeris data. (I may be wrong on this, but that’s how I understood it).
Good news is that in the same email, aeris / pwsweather seem to indicate that their data is now works better outside the US (more on this here).