"I have frequently pointed out to these people that if we do not revere Nichiren Daishonin as True Buddha then it follows that we cannot attain Buddhahood. It follows that if the one is not, then the other cannot be either." -- Nichiren Shoshu member
Logic is not the be all and end all of Buddhism but it does have a place in Buddhist teachings. This assertion is illogical and therefore does not have a place in the teachings.
Nichiren Daishonin worshiped the Eternal Buddha Shakyamuni of the 16th Chapter of the Lotus Sutra, the teacher, source, substance and entity of Namu Myoho renge kyo and the Gohonzon or as Nichiren states, "The Buddha who is the entity of Myoho-renge-kyo of the “Life Span” chapter of the essential teaching."
Therefore, what really follows is, if you wish to have the same Enlightenment as Nichiren Daishonin you must worship the same object as he. Your object of worship is not the same as his and therefore your Enlightenment is not the same. The SGI is even more deluded because they worship Daisaku Ikeda as the source.