/usr/local/share/fish/vendor_functions.d is not in $fish_function_path #11349

Fish version: 4.0.1
OS version: Debian Linux Trixie (Testing)

According to the manual functions should be autoloaded from the paths in $fish_function_path which should contain /usr/share/fish/vendor_functions.d as well as /usr/local/share/fish/vendor_functions.d.
Apparently this is not the case:

~> echo $fish_function_path
/home/me/.config/fish/functions /etc/fish/functions /home/me/.local/share/fish/vendor_functions.d /usr/share/fish/vendor_functions.d /usr/share/fish/functions

Both, $XDG_CONFIG_HOME and $XDG_DATA_DIRS are unset.

The XDG Base Directory Specification states:

If $XDG_DATA_DIRS is either not set or empty, a value equal to /usr/local/share/:/usr/share/ should be used.

Also the above mentioned fish documentation hints the same.

The same seems to be true for the vendor_conf.d directory:

~> echo $__fish_vendor_confdirs 
/home/me/.local/share/fish/vendor_conf.d /usr/share/fish/vendor_conf.d