Austria, like almost all continental Europe, is not a common law system and thus does not have an adversarial justice system where the judge serves as a referee between defense and prosecution. Very crucially, civil law systems do not have juries, and case law is generally not as important as statutory law.
Adversarial justice systems aren't strictly incompatible with civil law systems (see: Latin America largely dumping the inquisitive model in favor of the accusatory one in recent decades), even if most civil law systems do have an inquisitive system. It's the primacy of statutory law over case law that really separates civil and common law systems.
But yeah, the use of an inquisitive system really helps make it feel like Vienna is putting their thumb on the scale, regardless of whether that is the case.
(No, this has nothing to do with the fact I just started the Penal Process Law subject in college. Okay, it has everything to do with it)