Shiro Omiya claimed to be a student of Tsuruyama Kozui, who was controversial in his own right, but held a legitimate 8th dan from Takuma Hisa.
I trained with Tsuruyama's dojo in Japan for a number of years - he had already passed away, but most of the senior folks had trained with him for many years.
After seeing the Omiya book I asked the head instructor about Omiya and Omiya's relationship to Tsuruyama. His exact words were "Well, I guess that if you train with someone even once you could call them your teacher".
I know the translator of the Omiya book - he translated it only on the condition that his name not be attached to it. His exact words were "That guy was just making it up".
You have to be careful whose material you're examining.