Here is my understanding: Under Kellen, the team ran option routes. As the WR was going out, he would read the defense and adjust his route accordingly. Dak obviously had to make 3 reads, pre-snap, post snap confirmation and then once he chose a receiver, read which route option he was going to take. Many of the interceptions last year were situations where the WR and QB made different route option reads.
This year, the team isn't running option routes. The WR's just go out and run their play. Dak still has a pre snap read and post snap read but once he picks a receiver, he knows which way the guy is going.
I don't know how many teams in the NFL use WR option routes.
I see the pro's and con's of both systems. The new system is certainly less prone to error but you are going to get more situations where the receiver runs into coverage instead of out of it. This is going to make Dak's pre and post snap reads MORE important but take away the third read.
