This seems to be just a combination of having fixedTic enabled and running at too high graphic settings. Maybe remove?
Topic on Talk:Quake 4
I agree, the note should probably be removed. Noticed myself how certain scenes tank GPU, spiking utilization to 99% -- which results in excessive input latency. This is probably what author meant by "slow motion".
This is fixed by lowering anti-aliasing a notch and keeping FPS capped at reasonable limits [can confirm], which is generally common sense.