It's an argument that Daniel J. Bernstein made when proposing slashdoc. So M. Dickey is not alone.

* https://cr.yp.to/slashdoc.html

I myself write doco in Docbook XML

* https://news.ycombinator.com/item?id=15779321

generate HTML from that that can be read directly

    xdg-open /usr/local/share/doc/nosh/machineenv.html 

or on the WWW

* http://jdebp.eu./Softwares/nosh/guide/machineenv.html

and generate roff for man pages from it as well

    man machineenv

Whereas --help output is auto-generated from the option definitions given to the command-line parser, much like libpopt does.