I think it would make sense to have it default to 'Combine' in that case, since this is probably what most people expect to happen. You are obviously free to decide your own terminology as long as it's internally consistent, but it would probably help "ex. Freehand/Illustrator" folks like me.
On a side-note (which you probably already have in the works): The description of the selection needs refining. For example, a "compound curve" should probably be called such, rather than the more non-descript "curves".
JPCB got a reaction from Kal in Release compound greyed out for compound path