In order to get zone_name information, the programmer has to ask for it explicitly on the query string.  When programmers make mistakes, it's usually bad to ignore--it usually is an issue of incorrect assumptions.

So, better to point out the real error directl (the programmer is asking for something that's not available), rather than cause some other confusing error (they ask for something and it gets ignored, so isn't in the dict of what returns--which will also likely cause an error that they'll have to debug)

So I believe this should throw an exception--any time something requested is not available.