$XDG_CONFIG_HOME defines the base directory relative to which user-specific configuration files should be stored. If $XDG_CONFIG_HOME is either not set or empty, a default equal to $HOME/.config should be used.
$XDG_STATE_HOME defines the base directory relative to which user-specific state files should be stored. If $XDG_STATE_HOME is either not set or empty, a default equal to $HOME/.local/state should be used.
https://specifications.freedesktop.org/basedir-spec/basedir-...
[0] of course one shouldn't assume that a totalitarian decision is a mistake, because it's just as likely that the decision-maker has priorities other than "support users"
[1] yes of course users have agency with respect to where XDG is implemented, but the simpler rule would also have given them agency with respect to whether it is implemented
There is a single base directory relative to which user-specific data files should be written. This directory is defined by the environment variable $XDG_DATA_HOME.
There is a single base directory relative to which user-specific configuration files should be written. This directory is defined by the environment variable $XDG_CONFIG_HOME.
Neither of those environment variables is defined on a stock Ubuntu 22.04.1 LTS.