That's not a fair comparison, because we can distinguish very high frame rates (eg. 1000fps vs 3000fps) by watching how the perceived image changes in reaction

That's not a fair comparison, because we can distinguish very high frame rates (eg. 1000fps vs 3000fps) by watching how the perceived image changes in reaction to eye movement. Consider an LED strobing at 100Hz. This is above the flicker fusion threshold, so with motionless eyes it will appear steady, but if you flick your eyes from side to side you will see multiple images (phantom array effect). This is limited to some extent by saccadic masking, but never perfectly, and saccadic masking strength varies from person to person. Similarly, limited frame rate makes it impossible to keep the image at exactly the same place on the retina during smooth pursuit eye tracking, causing perceived blur that wouldn't be seen with a real life moving object. Seeing a difference with 1000fps video doesn't mean we have 1ms temporal resolution perception, it just means some test signals allow conversion of temporal information to spatial information by eye movement. It doesn't generalize to arbitrary visual events. To investigate keyboard latency sensitivity properly there's no substitute for ABX testing of actual keyboards.