It's likely that he meant she didn't use Six Paths Techniques/didn't know how to use them. I mean, they're called Six Paths Techniques for a reason; Hagoromo discovered them. Kaguya's attacks are generally kind of instinctual attacks based on her KKG (bone jutsus and dimension-shifting). In spite of having all the releases, she doesn't really use them in battle, for example. Mainly relied on Ash-Killing Bones, Byakugan, dimension shifting, that hand-thing...
6P's Rinnegan dojutsu requires some mastery, but Byakugan kind of just works (even though you can obviously increase your proficiency with it). Sharingan tech is the same, you can just kind of instinctively use the dojutsus.