I think one thing that trips people up is that your retina does not act like a CMOS sensor -- it doesn't sample snapshots of what's there all in one stroke, each rod and cone fire when they get stimulus, and then some time passes before each can fire again.

The underlying process is a protein that bends a bit when receiving a photon (it becomes another electron in the molecule, enough to make it change its shape). That electric potential travels down the optic nerve and the molecule returns to its previous shape. This takes time, but it's the firing rate of a single rod or cone, not a frame refresh rate for the entire eye. There's no vsync setting for human vision.

Our brains are structured and trained to make sense of this information more-or-less continuously so when 20+ milliseconds pass before any pixels are updated, the individual rods and cones all have to wait for the update rather than have new stimulus ready when they are.