Demonic Phoenix
Senior Member
Yes, insight is a Byakugan ability, but that insight is specific to chakra and vision, and not body movements. It can track movements, but it cannot auto-analyse those movements and predict the person's next movement(s) from that.
Analysing your opponent's body language is Neji's skill. None of the other Hyuugas have demonstrated that ability afaik, but no reason they shouldn't.
And we know Neji would be skilled at analysing body movements because he's the only Hyuuga who could learn their techniques via observation.
It's just like the Hyuuga focusing their Gentle Fist style on the Byakugan's ability to see the Tenketsu. Gentle Fist is not an ability of the Byakugan, but the Hyuuga. Neji analysing Hinata's body language is similarly Neji's skill which is aided/based on a Byakugan ability.
Or Itachi predicting Kabuto's movements when he could not see Kabuto, because he knew what Kabuto would likely do.
Whereas the Sharingan's precog is in-built and doesn't require analysis from the user.
So you did hit the nail on the head when you compared it to Gai's ability to track movements whilst looking at his opponent's feet. Because it's really Neji's ability to analyse body language, not the Byakugan's.