When you check websites like https://ipv6-test.com or https://ipleak.net while connected to Milan, Italy with Freedome for Android, both sites will recognize the ipv6 as being in the US. Only the IPv4 is recognized as being Italian.
I do believe that the problem you are describing might have already been addressed before:
This is a fairly common problem. It affects similarly our and our competitors and it is not tied to only one country. In this particular case, that particular server is certainly in Italy and the IP address is properly registered to Italy in the official RIR databases and all the geoIP data providers also list that IP address to be in Italy.
However, big companies like Google and Facebook do not rely on the official RIR databases but instead have their own heuristics (probably) on top of the RIR database information. They may have seen a number users coming from this IP address but they know from elsewhere that those particular users are in from the UK (they may have the location services turned on the phone and that reveals the actual location, or they simply may have registered to Google services that they're from the UK, etc). This information overrides whatever data they get from the RIR registry and POOF, they think the server behind our IP address must be in the UK.