I agree with you, somewhat. Even if those stats that you listed shows Taysom slightly better than Tanner, you left out what is to me the biggest factor: Taysom is a 5th year Senior and Tanner was a true Freshman that had only been home from his mission since June.
I would expect that Tanner has improved greatly since then with a full offseason. I also would expect that this offense "fits" Tanner better than it does Taysom.