His old shield didn't have a Sheikah symbol on it. It was just an eye. Lots of things in Zelda have eye patterns. I also don't think that the Sheikah symbol on that book means anything when it comes to him. It could literally be a Sheikah artifact and nothing more. Doesn't mean there are Sheikah in the game or that Link was raised by them.
Intriguing none the less.







