The publisher, in this case Postbank, decides what countries to allow installs from for an app. Google just enforces the policy the publisher sets.
replyCountry availability is a policy set up by the app publisher, not a Google policy
replyWhich is complete bullshit with the Euro having been specifically invented to be used across the EU.
replyI had a similar moment of stupidifiedment trying to park in Germany with a phone set to Dutch region. Euro in cash works everywhere Euros are accepted but apps on the freaking Internet? Nah, gotta restrict that to the publisher country only.