The non default bundled themese don't know about the new system.content.add web item location key (and probably others as well) that was introduced with confluence 2.8. Plugins that use this new web item will not show up in the non default themes.

If the old system.space.actions location is used with the default theme it also gets added to the menu so you end up with two web items, this means you can't use the correct location in the menu on the default theme and have the other bundled themes work correctly.