This may be true....but there has been noise that he was poorly coached and had a major flaw in footwork. Since he ended his college time, he made a change to his footwork and has been much more accurate in workouts. Also, completion percentage has a lot to do with WR's running good routes, pass protection, etc. I do find it funny that a kid, who throws, say, 600 passes in a season is a better pick if he completes 24 more.
What he does have is a cannon for an arm like no other.
That is what makes these evaluations so difficult.
I first noticed that the small difference between average and good in terms of baseball batting average. 150 for 600 is .250, an average hitter. 180 for 600 is .300, a good hitter. The difference is only 30 hits over the course of a season, or about 1 per week. So getting just 1 hit more per week is the difference between being average and good.
Similarly, as you say the difference between being average and good in terms of completion percentage is about 24 passes per season, or about 1.5 to 2 per game. Sounds small. But I guess it adds up and matters.