localectl set-keymap <MAP> 

doesn't change "XkbLayout" to "<MAP>" in /etc/X11/xorg.conf.d/00-keyboard.conf,
if <MAP> is already set in /etc/vconsole.conf
(KEYMAP=<MAP>). It does work if KEYMAP is set to a different value in
etc/vconsole.conf. I consider this a bug.

Example:

# localectl set-keymap us
# cat /etc/X11/xorg.conf.d/00-keyboard.conf
[...]
        Option "XkbLayout" "us"
[...]

<change KEYMAP in /etc/vconsole.conf from "us" to "de".

# localectl set-keymap de
# cat /etc/X11/xorg.conf.d/00-keyboard.conf
[...]
        Option "XkbLayout" "us"
[...]

<change KEYMAP in /etc/vconsole.conf from "de" back to "us".

 localectl set-keymap de
# cat /etc/X11/xorg.conf.d/00-keyboard.conf
[...]
        Option "XkbLayout" "de"
[...]