First of all, wp_list_cats() was already depreciated in version 2.1, which a couple of millenia ago. You should not be using functions which is marked depreciated. In all probability, the info regarding the specific function is almost always wrong as it is long time outdated. You should really develop with debug set to true. If this was the case, you should have seen the depreciation notice.
Regarding the codex and its documentation I can tell you that everyone with a valid wordpress.org account can edit/add/remove info from the codex. The codex is not upheld or maintained by the core developers, neither by a set team of experts. This does lead to incorrect info being added or even outdated info not being updated to the current version of WordPress.
It is really unfortunate that there are so much incorrect data in the codex, I can tell you that there are some pages in the codex which is absolute crap and completely wrong. Unfortunately, there isn’t many experts that takes part in maintaining the codex, and most updates are done by people that are not well versed in WordPress and its practices.
As with the SE stack sites, every user on wordpress.org are there as-and-when they have spare time, and it is out of free will to help others or update the codex. No one is getting paid for any type of service rendered on these sites.
The codex still stays a great resource for info, regardless of the some technical discrepancies in its info. It still however stays your own responsibility to cross reference documentation with the actual source code. The value of core source code can never be understated. And always remember, http://wordpress.stackexhange.com always stays a great resource of info, and is in most cases more correct that the codex.
One last request, if you feel confident that your info is correct, and you see something very wrong in the codex, feel free to correct that info. Just remember, whatever you update, WordPress is still stuck at PHP 5.2.voetsek, so all syntax that you use should be PHP 5.2 compatible