I would venture a theory that at least some smart people at 3rd party booking websites (expedia/booking.com type things) are making use of RFC8805 geolocation d

I would venture a theory that at least some smart people at 3rd party booking websites (expedia/booking.com type things) are making use of RFC8805 geolocation data published by peoples' last mile ISPs, for the netblock they're coming from, in addition to whatever 3rd party geolocation data feeds they're buying from services such as maxmind. https://datatracker.ietf.org/doc/html/rfc8805 https://datatracker.ietf.org/doc/html/rfc8805