That is curious. Where in the docs is it mentioned? If you mean https://cockpit-project.org/guide/latest/multi-host then it has a warning at the top saying "This feature is deprecated as of Cockpit 322."
If it's somewhere else let me know and I'll fix it.
Notably, it is listed as a feature on the main page:

Originally posted by @f1d094 in cockpit-project/cockpit#22225 (reply in thread)