We may have crossed paths yesterday. Mine was a clearance to Augsburg from somewhere around Mannheim. Clearly, it doesn't matter much to the Frankfurt controller who gave me the clearance. The question is more about what the Munich controller expects as I near Augsburg. In practice, I imagine the Munich controller would simply give me an instruction that suited him -- either a heading or an IAF, as he did in that case. But I did wonder, as I flew towards the 25 centrefix, if he thought "why is this guy not tracking to the airport?"
Another interesting direct-to-clearance here is something like "direct twentyone twelve" (got that one yesterday too....) which translates to direct 12 miles final runway 21.
Never heard that one, though it seems to be more common to issue direct to a waypoint on the RNAV transition (e.g. MA012), which is convenient for everyone.
Well that's true, but the point is that I want to know what the instruction means without having to ask. If it's ambiguous without clarification, it's not a very good instruction.