But couldn't any german-speaking person in the entire world read this information that he posted, not only members of the forum?
Yes, the thread about US- and non-German exclusives is accessable without being registered on KW. Seeing pics only works if you're logged in though.
So it was made public information but only to those who speak german?
Well, since it is a German forum almost everyone posts in German on KW. There was no intention to make it readable to German-speaking people only, but he didn't distribute the info to other forums. He isn't obliged to post it on international forums as well...
BTW: There are interesting forum-sections on KW that are only readable when you are a registrated member there:
these are "Themenwelten" (theme-worlds) subboards with pictures, customs, etc... These don't show up when you're not logged in.