I'm not instrument rated but my understanding is that with ILS, instrument approaches can handle multiple parallel runways precisely and therefore the pilot has the tools necessary to distinguish between a runway and taxiway when in instrument conditions. Someone please correct me if I'm wrong.
Let the investigation happen, but from the reported facts, this seems to be a pretty clear case of pilot error.
And I think you meant to say "raises the question" rather than "begs the question."