Old computers, before double-buffering and compositing, were fast. Single-digit millisecond latency from input to output was common.

Now it’s 30-ish years later and computers have not recovered the latency increase from compositing, double-buffering, and other attempts to make every frame perfect. If you are showing a frame on the screen that has failed to react to input that already occurred, especially more than about 20ms later, that frame is not perfect. It’s extra imperfect if the user cannot easily do what they’re trying to do while waiting for the computer to catch up with them.

But yes, most of the examples in the article are surely both imperfect in the sense the author meant and pointlessly slow, so there is no dichotomy :-/