User blog comment:BlackWizardZeref/Fairy Tail: Chapter 436 Memoirs Review with a brief mentioning of Chapter 435 Victory Shout!/@comment-77.194.131.45-20150519091211/@comment-26416024-20150519221052

I have 2 explanations for this. 1. E.N.D. has a more demon looking form he can take that leaves his human form unrecognizable. Think the difference between Mard Geer's more human looking form compared to his Etherious form. Or 2. No member of Tartarus actually saw E.N.D.'s powers and memories get sealed in the Book of E.N.D. and assumed his body was also sealed away and therefore only sees Natsu's similarities in appearance as coincidental.