gtk-engines-xfce and confusion regarding gtk3

[transpetaflops]

My reference is the Xfce wiki page https://wiki.gentoo.org/wiki/Xfce
Especially the section regarding gtk3 https://wiki.gentoo.org/wiki/Xfce#Consistent_GTK.2B_3_themes

When I install xfce-base/xfce4-meta the ebuild is hardcoded to pull in slot 0 of gtk-engines-xfce which is revision 200. The ebuild has no logic for IUSE="gtk3". Emerging x11-themes/gtk-engines-xfce manually, after installing xfce4-meta, pulls in revision 300 in a new slot but nothing depends on it. Greping through the whole of Portage, I can't find a single ebuild depending on revision 300. Unmerging revision 200 at this point just results in it being reinstalled again during the next @world update.

What am I missing here? Have I misunderstood that revision 200 is for gtk2 and revision 300 for gtk3? How do I make use of Xfce and gtk3?

[blopsalot]

are you talking about GTK+ or wxGTK?

to answer your question though, XFCE in the main tree is out of date. unmask the 9999 builds in the xfce overlay
https://gitweb.gentoo.org/proj/xfce.git/

[transpetaflops]

As per the link to the wiki page I'm talking of GTK+. There are no 9999 versions of Xfce in Portage but I can see that some of the ~ keyworded 4.13 ebuilds have dependencies to x11-libs/gtk+:3. However, as I mentioned in my OP I still haven't found any ebuild in Portage depending on x11-themes/gtk-engines-xfce:3 which makes the wiki page confusing to me. The issue isn't vital to me in any way - I'm just interested in how things co-exist and interact in the system.