I've played with briskets A LOT. I found that if I foil it, pull it at temp and cambro it immediately I get at most a 1 degree rise if any.
Now, I don't know why it doesn't carry over cook as much as say prime rib that you are cooking to 125 and pulling to rest for 10 - 30 min but I have an idea. I believe that with a brisket in foil that the internal temperature of the meat and the external temp of the meat is so close that the exterior isn't hot enough to transfer internally. That prime rib is typically cooking at what 250 - 500 degrees depending on the method so the exterior is much much hotter than 125 and that's why you see a 5-8 degree temp rise with roasting like that. Brisket is typically 220 - 275 and that isn't enough to allow the rise. Now cooking hot and fast may be another issue entirely.