>Anything that takes less than 200 ms is perceived to be instantaneous by the human brain

Negative, ghost rider. What is perceived as instant depends on a lot of things, most studies in the past arrived at a threshold of 100ms, but there are domains where 100ms will feel horrible (first person gaming, VR tracking, conversation audio, etc). We know the brain can see things that are visible for only 13ms:

https://news.mit.edu/2014/in-the-blink-of-an-eye-0116

When I am programming if something that doesn't require IO takes even 1ms I immediately take a look and make sure something isn't wrong.