Just out of curiosity, where did you get this info about the claims?
I'm grown up in germany, and everybody (that includes also politicans/newspaper etc..!) allways told that we live in the "new" borders and the old ones were obsolent with the war and at least with the "Treaty of Moscow (~1970)".
The only "open" question was ever officially only the reunification with the GDR(DDR).
Why they over and over again in treaties pointed out the "new" borders is beyond my knowledge. Last time was the reunification treaty in 1990..
So, maybe that was handled/told different in other countries?