yes, it's not all skins, but very many skins, eg. DarkRED3/DarkRED, DarkRED Flat, Dark-Metro Series/DarkRED, Pastels/Azure, Arsenic, etc. Maybe they must be updated to work in mb 3.5
Using a piggyback skin will probably make it possible to display arrows for the scrollbars for .xmlc skins that don't have them.
E.g. creating a "DarkRED arrows.xml" like this should work:
<?xml version="1.0" encoding="utf-8"?>
<root dependsOn="DarkRED.xmlc">
<element id="ScrollbarNoArrows">false</element> <!-- true/false -->
</root>