Interesting. Can’t explain why you get the confirmation. I thought the issue was a result of the switch to systemd for user login. Isn’t Xubuntu using systemd for user login in 18.04, btw? Would be good if we could figure out what’s going on.
I agree on that, and like you I’d like to get the word out.
However, Ubuntu’s guest session is known as a feature which allows you to enter a restricted guest session. That was true as long as the AppArmor profile worked as intended, but the guest session is currently not more restricted than any standard user (leaving your Xubuntu observations aside for now).
With that said, it’s a feature which allows you to enter a session as a temporary user, and everything is cleaned up when you log out. That’s indeed useful in many use cases, and many system owners can live with the absence of the extra security which AppArmor used to provide.
So I really don’t want to discourage you from informing about the guest session. My point is that it’s important to be correct with respect to the AppArmor protection.