I came across this, apparently Sakura was born with precise chakra control. It is what allowed Sakura to master Medical Jutsu and we know precise chakra control is the source of CES. It would explain why Sarada who can use CES , she was likely born with that precise chakra control just like Sakura. It would be her inherent quality and removes any possibility of it being called an ass pull.
Edit: that's the databook entry for Sakura from Naruto the Last.