That's actually a pretty close guess. In order to get to the measurement capabilities that we needed, we had to build our own internal systems. Some of those systems had a small mention in this public talk:
https://www.youtube.com/watch?v=kyu_wDcO0S4&t=7140sThere are several major issues when trying to measure network paths in real time, but one in particular is how to avoid the assumption about path latency related to RTT/2. The latency of a path one direction rarely is half of the over all round trip latency, usually there are a combination of things that cause path asymmetry.
Anything you or others would like to know more about in terms of network performance measurements?