instead of taking aggregate statistics to try and prove your conclusion. Beck only started 10 games as a sophomore and threw 170 less passes. His stats would be this if compared apples to apples with the same number of attempts:
Sophomore: 3,847 yards, 23 TDs, 12 Ints (5 wins)
Junior: 3,709 yards, 27 TDs, 13 Ints (6 wins)
That looks like a slightly improved quarterback to me.