It's not just a MasterCard. There are still shops that will accept Maestro and not MasterCard. Further, some girocards, like mine, a V-Pay cards, Visa's equivalent, and not co-branded with Maestro.
Those cards that actually use the "ec" brand (rather than girocard) are proper debit MasterCards. You can see this on MasterCards German website [0]. Some banks are also using that branding to issue cards [1].
Beyond that, there are some girocards which are co-branded not with Maestro, but with MasterCard proper [2], although that is also unrelated to my previous statement.
[0] https://www.mastercard.de/de-de/mastercard-fuer-sie/finden-s...
[1] https://www.consorsfinanz.de/banking-service/kontakt/geld-ei...
[2] https://www.it-finanzmagazin.de/girocard-mit-co-badge-master...