Board Thread:Theories and Speculation/@comment-32742265-20180119154238/@comment-6769189-20180126063822

Sasuke was in pain because of the curse mark not the taijutsu.

The only nature Kakshi confirmed to learn himself was lightning and he said most jonin know 2. Sending Naruto to Asuma actually makes it more likely that Kakashi learned wind via the Sharingan because he would have bypassed most of the learning process while Asuma would have first hand experience learning it like a normal person and could explain it better.

Sasuke and lightning release could easily have been a stamina issue or because his Sharingan was incomplete. but he learned the fireball jutsu at a very young age. He didnt "just know the seals"