r86861 (the fix for bug 24298) was followed-up by r99083 which made the feature more generic by applying it to any vectorMenu (instead of just p-cactions).
If this is not working on the language variants menu, perhaps it doesn't have the "vectorMenu" menu class. This would presumably cause other problems as well.
Checking SkinVector.php I see both p-varians and p-cations have class "vectorMenu" set. So it should be working.
It isn't working because I9a2ebd503e change the current-variant heading and the dropdown arrow heading (h4 and h5 respectively) to h3. And the script looks for the first h3 in a vectorMenu, which as of I9a2ebd503e is no longer the heading with the trigger in it.