Not really. Dak Prescott made a big leap in 2014 going into his redshirt junior year. Brandon Allen made an even bigger leap in 2015 going into his redshirt senior year.
Go look up their stats. I actually made a thread about it a few months back. QBs make these big leaps very often from the 3rd to 4th year in a system. Allen was a little late waiting until his 5th year to make the big leap.
If we're simply talking passing stats, Josh is ahead of where Dak Prescott and Brandon Allen were as 3rd year players last season.
Yes, really. You gave two examples, which are flawed examples as I'll point out next, and two examples are hardly any type of proof that the type of leap we're discussing is anything close to common. As for your two examples, you used Dak's 2014 season, which was his second year as a starter. For Brandon Allen, you used his 4th year as a starter. Neither of those leaps are comparable to the 3rd year as a starter comparison you made between Dobbs and VY. You simply cherry picked two examples that you thought fit your narrative, but in reality, they aren't the same comparison. The fact that you only gave those two as examples pretty much shows just how uncommon such a leap is.