My ass, mostly. I'm extrapolating based on monitor framerates and how accurately we can see the velocity of fast-moving objects, and that I can spot a timing difference of ~5ms reliably.

Human eyes are almost comparable in terms of a framerate based on the neuron spiking rates, which are somewhere over 250-500Hz max. Obviously that's not directly comparable though, but it gives an idea of how well we can deal with moving objects.

I think they're pulling it from noticeable monitor FPS rates. I'm not an expert on machine vision, so I couldn't tell you the FPS needed to correlate movements between frames.