Maybe Bp. Williamson could not distinguish an east or west German accent?
It's indeed very difficult for people who don't speak German natively, to distinguish this.
Interestingly, Maximilian Krah, Bishop Fellay's lawyer and financial advisor
was educated in a Dresden primary school owned by freemasons.
Although Krah was raised in the communistic East Germany -- in the county Sachsen (Saxonia) where the town Dresden is --, he does not
speak the nice Saxon dialect, which Germans would recognise normally. Krah's spoken German got elements of a strange dialect.
P.S. Your link to a comment about the professor's face, doesn't seem to work for me.