The whole ta’do about how the second Death Star got built so quickly could be solved by the Seperatists already making one by the end of ROTJ and the Republic making their own based on stolen plans.
The two could be confused in the chaos of the Galactic Empire rising so when the one in Rogue One got all blowed up the Empire just turned it’s attention to completing the other one.
Having Starkiller Base turn out to be Naboo would be a rather twisted way of turning the PT and the ST in on themselves.