The article refers to a previous, in which the author wrote
German soldiers issued an Enigma were to make no mistake about their orders if captured: Shoot it or throw it overboard.
Actually the Germans went on the assumption that the Allies had the machines (like modern cryptographers assuming the details of an algorythm being known), it was the day codes that were jealously guarded.
Also like asymmetric crypto used to encrypt the secret key used to actually encrypt a email message, the Enigma day code was used to encrypt a specific one-time code (the scrambler settings) used to encrypt the message.
Given that the Allies were able to consistently obtain the day codes, it seems strange that, as far as I know, the Allies never took advantage in order to send a fake message (I expect that, for the Germans, a properly encrypted message would have had better bona fides that otherwise). Presumably the risk of the Germans clueing in (and changing how Enigma was used) was deemed too great.