Thats true. Very few second year players are great leaders. Peyton Manning took a few years also.
To me, a sign of a great leader on the field is someone who show constant steady leadership. The highs are not too high, the lows are not too low. You take everything with a short memory and move on to the next play. Right now Cam is celebrating touchdowns like it is his first, and sitting by himself on a bench after an interception, not wanting to talk to anyone or review the play. He is all over the charts emotionally.
Players need to see a leader who is even keel and ready for anything that gets thrown our way.
Great players establish themselves as leaders early in their careers. I agree with everything else that you wrote.