You still haven't explained
I found an interesting scientific study (in German unfortunately, but written by a famous Polish-German scholar Dr. Andrzej Kaluza) on this issue:
It makes a lot of interesting claims that I could partially validate.
One of them concerns the often repeated claim that Poles enjoyed "minority rights in Weimar. This is in fact not really true, at no point does the Weimar constitution state that. Article 13 merely states that no minority should be surpressed in their cultural identity, but that does not imply minority rights as we would understand them, which means the active support via the state (e.g. financing the teaching of their language). It was forbidden in Weimar to e.g. force a child to abandon its' Polish native language, but the state was not required to provide it with opportunities to nurture it. And there is no other legal document that could be interpreted as granting the Poles minority rights. (The analysis mentions two other documents that have been brought up but thoroughly debunks them, if necessary I can come back to them later but as of right now I am too lazy to translate the complicated terms). So saying that giving Poles minority rights would restore them rights which they lost under Nazi Germany is de factor false. Mind you that was something Polish Germans criticized from the very beginning, and which is why those Polish minority rights groups formed in the 1920s.
There is also an important legal argument which I shall quote here in case I mistranslate it:
Es handelt sich dabei um Gruppen von Menschen, die eine eigene nicht-deutsche Identität besitzen, gleichzeitig aber das Gebiet des deutschen Staates seit Generationen bewohnen. So haben z. B. die Dänen Minderheitenrechte, die ihnen ein deutsch-dänisches Abkommen von 1955 gewährt, die aber zumeist nur auf wenige Landkreise in Schleswig-Holstein beschränkt sind; ein aus Flensburg stammender Deutscher dänischer Herkunft kann dort einen dänischsprachigen Kindergarten für seine Nachkommen verlangen, nicht aber in Berlin.
Basically only groups which are acknowledged by international law, and who still identify as such and who lived in Germany for generations can enjoy special privileges tied to the area they live in. Which is why Danes have privileges in certain parts of in Slesvig Holstein, but not e.g. Berlin.
Since "Ruhrpoles" were never a specific minority group recognized by international law, and by 1945 can hardly be said to still have formed a distinctive group, this no longer applies. All Poles arriving in Germany after 1945 are thus treated as any other migrants.
It is also worth noting that (at least until 2011 when this was written) the only group who consistently used the legal term "minority" were Polish lobby groups, even Polish politicians have not used it with its legal implications. The German interpretation has apparantly been upheld by several courts. The reason why this was never brought before an European court is that most Western European countries do not recognize minority rights to begin with (hence why other countries with many Polish migrants do not even contemplate this).
This is only up to page 2 out of page 4, I'll translate the other parts at a later time.
I really would not recommend this one. This site is dominated by right-wing radicals,