It doesn't really explain much about its purpose. Is it better than libavcodec? I take it that the point is to re-use techniques from the h264 encoder for encoding MPEG-2 where applicable?

Handy for those four people left who want to author DVDs, but this is extremely light on details.

How does it compare to the venerable HCenc[0]?

Why does the VideoLAN x262 project page[1], the source for which hasn't moved since 2015, also link to a 404 wiki page in this Git repository?

It looks like perhaps this is an old repo which has recently been rebased onto a newer (but still not particularly new) revision of x264. It is very unfortunate that whoever did the rebase did not retain the original author dates (perhaps even having gone out of their way to --reset-author-date).

0: http://hank315.nl/

1: https://www.videolan.org/developers/x262.html