https://www.youtube.com/watch?v=RfYspQaxPp0

In this video, Mystery talks about why we may fear approaching women, and how it is irrelevant in modern society, and perhaps why old PUA community came up with the three second rule.

EDIT: In addition to this, here is another video of Mystery talking about what 3 seconds rule is https://www.youtube.com/watch?v=lXCxHtXoVMc