> From what we understand, when a large number of users from a censored country use a specific VPN provider, Google's device-based signals can bias the geolocation of entire IP ranges toward that country.

Yep, this is a known effect.

How it seems to work is: Google uses Android phones as data harvesting probes. And when it sees that a lot of devices in a given IP range pick up on GPS data, Wi-Fi APs or cell tower IDs that are known to be located in Iran, and possibly other cues like ping to client devices or client device languages, timezones, search request contents, then the system infers "there's a network wormhole there with Iran on the other end", and the entire IP range grows legs and drifts towards Iran.

The owner of those IP addresses can mitigate the issue, mostly by shaping traffic or doing things to Google's system, but I know of no way for anyone else to do it.