EXCEPT for the fact that Quinn won't start right away and might even be redshirted
If you think Quinn thinks for a minute somebody will beat him for the job you don't know Quinn.
You don't catch 120 passes for 2k yards in a single high school season because you think somebody might be better than you.
For somebody like Quinn, the concern will be more about "If I'm the best receiver in college football, will the offense use the receivers enough for me to get my due?" A competitor like him, you put 15 5 star receivers in a four-week training camp with him and he'll think he's going to emerge as the best one.
All that said, again, I think LSU is in great position with the kid. They simply have to ease his mind about the passing game and how he'll be used in it.