Right, I didn't quite figure that out when making my comment.   Seems like a use case that is potentially more common that just this case.  We can distinguish the case, right?  Once the *structure is used to create a card, the card become "real" as well.  The cases where cards with *structure rules "always exist" are mostly where the rule is a Search card, right?  In all cases where the *structure rule would need to create a real card for it to make sense (typical template with +cards), they have to have permission to create (like the needed permission on +*account card creation).  We have special handling for this idea with Cardtype to not offer the types they cannot create.