Yes, I've seen stuff like that. In a guide for IVPN a couple years ago, I looked at a few examples more carefully. I say more about that in this subthread.[0] One of their network engineers helped me understand what was going on with their servers in Zurich, Reykjavik and Salt Lake City. As I recall, we found that two of their Swiss servers, in different data centers, had no direct peering. One peered with the other via Milan.

I also played around with placing my own probes, using VPS hosting that peered with VPN server hosting. Using information from https://bgp.he.net/. But that's too tedious for general use.

In this work, I basically ignored it. And focused on testing for plausible signal velocity.

Still, I do agree that it's an interesting problem. Maybe I can learn enough to make it doable.

0) https://news.ycombinator.com/item?id=21932436