Well, maybe so, but I have a choice at the Session selection of KDE, Gnome, WindowMaker, Default, etc. Default, is BlueCurve, or so I thought. And I thought BlueCurve was a sort of cross between KDE and Gnome, or something. But it sure looks like Gnome.
Anyway, I logged in and specifically selected Gnome and the PrintScreen key worked there also as I described.
edit: I've also used Gimp for screenshots and for shots of specific windows on the desktop.