They say that they don’t have a minimum speed requirement and the speedtest result doesn’t affect your application. Also considering that they specify that you choose the node geographically closest to you (instead of the lowest latency one) and the only other information in the test is latency, it does sound like they’re either looking for vpns or your location.
IP is quite unreliable when it comes to geolocation, especially if you have a dynamic ip
Did YouTube decrease the bitrate again?