The reason the offense feels "slower" to folks is because less of the play this year are successful, leading to more stops and starts and less of that tempo where Tennessee ran to the line so fast they could snap the next play before the opposing defense was set. Hooker completed about 70% of his passes, and Milton hits about 63% of his -- that 6-7% difference is huge. If your passing game is hitting 7 out of 10 passes, your offense is ahead of the chains and probably running the opposing defense off the field. More completions, more quick strikes, and thus it feels "faster." Tennessee is still running a lot of plays but it's just a bit less successful.
And look, this ain't a "Milton bashing" thing, 63% is still pretty good and the guy's our starting QB. But Hooker was giving us Heisman level QB play last year, and that makes everything click more smoothly and more quickly.