In a way I did say if he wants something “lighter” than XFCE. I should have said “You have to start with something like XFCE, gnome, etc. Just to get your the general feel of linux” Then if you wanted something lighter you can try dwm.
He can easily install dwm, or any other wm and choose it from his log-in page. If he doesn’t like it he logs out and chooses another ones that suits him well.