I travel between different countries every now and then and sometimes need to install apps that are only available in a given country. At least for that case, Apple uses your billing address, which is verified by a payment method. E.g. you need a Dutch domiciled payment method to configure your app store location to be the Netherlands and install apps that are available to locals only. These days many apps are available without geographic restrictions, but far from all. I would imagine they use a similar setup for the whole EU only perks.