When i started using GuixSD i wondered about this strange message, but i soon accepted it to be normal behavior.
In fact i became relived every time i see it appear when booting because it meant i did not break my system to much while tinkering around.
I recently did an upgrade to 1.4, and all of a sudden it was gone.
I was so startled that I've been spending hours reading logs hoping to figure what was causing this error message in the first place.
I thought i would never solve that mystery until i found this thread.
IMHO this message should persist.
As long as it is possible to disable and documented in the handbook this is not worse than putting some quotes in /etc/issue (like a majority of distros do).
Also the stickers make for a great wallpaper and i hate to change it anytime soon.