Comment 13 for bug 1274740

gnome2/compiz sessions such as flashback and cairo-dock, should really not be using "GNOME", this is mostly gnome-shell specific.

GNOME Classic, should probably be using "GNOME" since it is gnome-shell based. Although that makes it impossible to have different behaviour in classic vs gnome-shell.

Using anything other than Unity or GNOME should work, however I suspect there is some fallback to gnome2-ish behaviour lumped under "Unity", especially in cases where the default upstream GNOME3 behaviour has changed significantly.