The speed of light provides a limit on distance for a given RTT, and taking the examples in the article which are less than 0.5ms and considering the speed of light (300km/ms) the measured exit countries must be accurate.
The speed of light in fiber which probably covers most of the distance is also even slower due to refraction (about 2/3).
Thanks for your informative reply. I see now I was approaching this incorrectly. I was considering drawing conclusions from a high RTT rather than a RTT so small it would be impossible to have gone the distance.
The speed of light in fiber which probably covers most of the distance is also even slower due to refraction (about 2/3).