Dunno if the story was a scare story to ensure you either did jobs correctly or had a "Cant catch me sig"
to prevent any visits at a later date....
Just before I left I worked with an engine chief that had two signatures, one his Civi one and one his RAF one.
He told me one day that as a joke when he joined up he signed everything RAF with Rastus, and had continued to so for his whole career, he said no one had noticed, and when we checked a few of his sigs, sure enough they all read Rastus!