That's not quite what the rule tries to accomplish. Rather, the point is
this: personal data being public does not allow anyone to aggregate such
data in a way such that the result is still tied to individual people (also
called 'profiling'). Why is that so? Because according to this German point
of view, people have the right to control what their personal data is being
used for. Since, when setting up an account on MediaWiki, there's no
explicit statement saying that your editing data may be aggregated in such a
manner, MediaWiki users didn't give permission to such aggregation and
therefore such aggregation may not take place. Therefore, such aggregation
without opt-in can't be published on German Wikipedia or on the Toolserver
(which is run by Wikimedia Deutschland and therefore subject to German law).
I understand that this position may seem odd to a lot of people, especially
if they come from the US or UK. I'm just stating a perception that is very
common here.
That isn't odd to me. Where does anyone sign to give permission for
their editing history to be aggregated and scrapped? There is no such
permission granted, and as many are under 18 they do not have the legal
capacity to enter into such agreements anyway.