Board Thread:Versus Debates/@comment-26479810-20200120120035/@comment-9782468-20200122005421

There's nothing saying that Kaguya would know Momoshiki's abilities; it's not enough that they were part of the same clan. Sasuke was part of the same clan as Itachi and didn't know all of his abilities.

In any case, we see that Momoshiki can absorb Ninjutsu and throw it back at several times the power. When would Kaguya ever see that happen? Ninjutsu is a concept created on earth. Even just counting chakra, only the Ōtsutsukis had chakra, and they weren't enemies yet. There's no reason for her to know his abilities.