So why does /sys need to exist? What it does looks clear to me: provide a shortcut to /usr/src/sys, but why is (or was) one needed?
(In reply to PauAmma from comment #1) Via <https://old.reddit.com/comments/giaz0j/-/fqeekss/>: Unix directory hierarchy history | Pixelstech.net <https://www.pixelstech.net/article/1477109665-Unix-directory-hierarchy-history> (2016-10-21) The response in Reddit compared these two manual pages – /sys/ is documented in the first but not the second: <https://www.freebsd.org/cgi/man.cgi?query=hier&sektion=7&apropos=0&manpath=2.11+BSD> <https://www.freebsd.org/cgi/man.cgi?query=hier&sektion=7&apropos=0&manpath=4.3BSD+NET%2f2> If I recall correctly, the symbolic link is for compatibility and not purely historic.
I guess, symbolic links are intentionally excluded from hier(4). If so, document them in the FreeBSD Handbook: <https://docs.freebsd.org/en/books/handbook/basics/#dirstructure> <https://docs.freebsd.org/en/books/handbook/book/#dirstructure>
Sorry, a typo: > hier(4). – I meant hier(7).