The problem is that EU regulations (which you are no longer subject to, but hear me out) require that a buyer's location (country) is determined by at least 2 independent methods (to assign the correct VAT rate).
In Dominion Online's case, the first method is some geolocation software that maps your IP to a country and the second method is you answering the question.
In your case (and some others), the geolocation software is giving the wrong result for unknown reasons
Since the geolocation software thinks you are in the EU in oth cases, it wants you to confirm it. Now you can choose if you want to buy "out of Greek" or "out of Germany".