My first impression is to be careful about placing BotW and TotK in a specific point in the main timeline. That aside he does not have the same body as from OoT. We see the Gerudo serving Ganon in Rauru's time as a regular Gerudo. He does not yet have the power that usually belongs to Ganon...
Impa is the only Shiekah present at the time of the original Legend of Zelda. It is unlikely that another Shiekah is alive, however there are no other Shiekah mentioned in the game. If Impa were to teach a non Shiekah these skills, it would be for an important reason. The only time this is seen...