Your first point is fair enough, it is not the "simplest" substitution cipher one could imagine (one-to-one mapping), but I would say it's still a fairly simple

Your first point is fair enough, it is not the "simplest" substitution cipher one could imagine (one-to-one mapping), but I would say it's still a fairly simple mapping. The reason I mentioned that none of the researchers speaks German is remarkable in two senses. First, it is the only reason they had to use machine translation in their approach at all! It was only for their testing the quality of their intermediate results, and not - as theregister suggests - a central part of the deciphering. Second, the fact that you don't have to speak the target language gives some credit to their methodology, because to some degree there's hope that the complete algorithm could be automated.