It's put me on the wrong continent before now. That was fun.
Just because it’s 800km off for your IP does not mean it’s 800km off for every IP and Maxmind is generally considered one of the reliable providers of this information.
I believe my ISP rarely or never rotates IP addresses, and on top of that I think my ISP provided router is assigned an IPv6 address and it prioritizes using it, because when I visit whatismyipaddress.com with JS disabled, it can only show my IPv6 address, but if I enable JS it can show an IPv4 address too (I assume through the WebRTC IP leak method, which requires JS)
I don't think they need any hackery to get your IPv4, they just need a separate hostname configured that they can fetch from, which only has an ipv4 (A) record.
What did you expect after leaving Europe? /s
If the location data is incorrect, you can always submit a correction with us: https://ipinfo.io/corrections
At my last job, I built a little docker image that used the free maxmind DB and kept it up to date, and ran a node server which returned some JSON telling estimated lat/long, city name, country, etc.