lucy24 - 1:10 am on Apr 12, 2013 (gmt 0)
Judging by the thread at google, you are not the only person to wonder. But the newly posted change applies only to the specific term "x-default". Other stuff involving "hreflang" was addressed earlier [support.google.com].
If you have several alternate URLs targeted at users with the same language but in different locales, it's a good idea to provide a generic URL for geographically unspecified users.
So if your assorted Germans all end up on the same page, there's no need to specify a region in the first place. Just 'hreflang="de"'. The region is always optional.