A normal high priest offers sin offerings for himself, because he is subject to the same weakness as those he represents. Jesus is sympathetic (Heb. 4:15), but without sin. He himself is the sin offering.
Jesus learned obedience through what he suffered. He brings eternal salvation to all who obey. I don't think Jesus learned in a way that suggests he was disobedient until he learned to become obedient. He learned, or was tested and passed, when he suffered.
You and I have an obligation to grow up to know the Scriptures. God has in mind a trajectory that each person should be on in the same way a healthy child moves from milk to solid food. Apparently, this group was lagging on account of laziness. Growth comes from reason of use. Practice makes perfect when it comes to handling the word and making mature spiritual decisions.
The $64,000 question is this: How can I speed up the process of that kind of growth? This text suggests two things, experience and practice.