hicolor-icon-theme ebuilds should be using gnome2-utils.eclass instead of gnome2.eclass to prevent inheriting unwanted functions, including this USE flag. be noted that hicolor-icon-theme-0.10 is also out, and worksforme without the patch that was used in 0.9-r1 with xfce4-4.4.0 in tree.
Switched eclasses. Thanks.