ALL NETWORKS have perceptible jitter due to this, unless you rigorously apply FQ and AQM techniques to each slower hop on the path

Fatter tests like waveform show the common bufferbloat scenario in ways humans can see, better. But slow start overshoot is always there, on any connection that lasts long enough, which only takes a couple RTTs. You can clearly see netflix doing you in here, for example...

https://www.youtube.com/@trendaltoews7143

(except that in this case, the link has libreqos and FQ on it, so all that buffering is just local to the netflix flow, invisible to everything else)

Joking aside, the https://www.waveform.com/tools/bufferbloat test looks to see if the networking software is working correctly by putting a large load on the network, and then seeing if other streams are affectec by the overload.

The example on the https://libreqos.io/ home page is of * good software delivering 9 and 23 milliseconds down/up latency at full load * bad software delivering 106 and 517 milleseconds latency under load.

It is, in effect, a test for software failure under load