WM_HINTS input focus ignored after window launch

Applications/Windows which do not normally accept input focus do not appear in the window-list used by alt-tab for cycling/raising. They will appear if Settings/WM-tweaks/focus/Honor standard ICCCM focus hint is turned off. However, this means all such windows will appear in the list. If one wants only one such window to appear in the list, one needs to turn on the WM_HINT for it, e.g.

xprop -name xmbmon -f WM_HINTS 32i -set WM_HINTS 3,1,1,0,0,0,0,0,0

This sets the hint properly, but xfce seems to ignore it. See the discussion here