This is/was also my take. I’m skeptical that a probe-based network can be granular enough to reliably pinpoint a city, especially when some paths are much better connected than others (fewer hops, uncongested fiber, no throttling).

However, ipinfo still appears to rely on active probing to triangulate geolocation data, which suggests they believe these routing asymmetries can be modeled or averaged out in practice.

https://ipinfo.io/blog/ipinfos-probe-network

yeah, when i used to live in New England, and had more time to be interested in transit, i always was peaked in how comcast would route. No matter how far south i seemed to get, i'd always need to travel to Boston's peering point first to make it to NYC, even in New Haven. If you then simply switch isps, even at same address, verizon would send you south immediately.

so theres funky overlap wherein on one isp you appear closer to city A, and on isp 2 closer to city B, but its same physical address.

Continental classification I'd think would be good as they appear to be coalesced endpoints, separated by vast oceans.