Board Thread:Naruto Discussions/@comment-34190103-20180104204528/@comment-25122992-20180106144034

Well, I'm actually not a fan of the filler events too, if you wanna know, but BZ is a being whom you can expect some sort of special abilities from. I mean, doujutsu is obviously needed for reading the Hagoromo tablet as well, while BZ wasn't just able to read it, but overwrite it as well.

Plus, just saying, filler aside, Hagoromo still told Naruto about the birth of his sons only after the story about the battle against Ten-Tails. So, it's only logical to assume they were born when Kaguya wasn't present anymore.