I was thinking of Clarence standing alone in its own right when I referred to William IV's title before he inherited the throne MOR.

Albert Victor was "double barreled" so to speak as he was Clarence and Avondale.

You raise an interesting point about the use of Scottish titles in Scotland. Apart from Rothesay (and Edinburgh of course) I am not aware that Prince Andrew, for example, is anything but Duke of York rather than Earl of Inverness when in Scotland.