Time of flight from three points gets you two options for position with GPS, but GPS signals propagate directly in free space. At least mostly, reflections happen.

Internet signals generally travel by cable, and the selected route may or may not be the shortest distance.

It's quite possible for traffic between neighboring countries to transit through another continent, sometimes two. And asymetric routing is also common.

Since this is using traceroute anyway, if you characterize the source nodes, you could probably use a lot fewer nodes and get similar results with something like:

a) probe from a few nodes on different continents (aiming to catch anycast nodes)

b) assuming the end of the trace is similar from all probes, choose probe nodes that are on similar networks, and some other nodes that are geolocated nearby those nodes.

c) declare the target is closest to the node with the lowest measured latency (after offsetting from node charachterized first hop latency)

You'll usually get the lowest ping times if you can ping from nearby customer of the same ISP as the target. Narrowing to that faster is possible if you know about your nodes.