Build date was 08/19, but have since traded in for a 3500, build date of 09/20 and they both behave the same.
Just came back from a trip in the mountains, pulling my trailer and I will agree grade braking works great, but on level ground, it is just not assisting. Its clearly the programming and if they would just reprogram it to downshift on level ground when in tow mode and EB on, it would make such a difference... IMO