as described you can see in this picutre, that i was moving my mouse "fast" in the beginning, and slowed down a bit no long after
the mouse is a pulsar xlite v2 wireless using the PAW3370 sensor, if im not mistaken.
EDIT: an example of what im talking about, i dont know of this is normal or not
another edit:
i tried doing the same exact testing on the zowie tester, and the test shown in my video with a Logitech G pro wireless, i bought on release day, so it has some years and use behind it. super slow speeds, and slow speeds only dipped to 450hz, but on the other hand it would go up to 2190hz at high speeds (see picture)
it would however have alot more "desync" between pointer location, and mouse location, like shown on the green and red highlight. note that this is a test made from the exact same kovaaks scenario, which i played on the video in my previous edit.
LAST EDIT:
contacted @RealDrunKev on twitter, and he sent me some commands i put into CMD, which made a static speed pollingrate go from fluctuating upwards of 500hz, to only 20hz. he later sent a few other commands, which lowered this value even further, to only 5hz in fluctuation!
Ignore the red box, it is consistently red for every single update, since i changed pointerspeed in windows to 8, rather than 6(default), so its on purpose. did the same test with default pointerspeed settings, which gave same results, but without the red highlights ofc.