I believe the internal temperature of the brisket should not drop below 140 degrees. It's my understanding that anything below that temperature for a long period of time bacteria will start to form and it is no longer safe. I could be wrong as I often am but that is what I've been told. I have kept my brisket in a warmer set at 145 degrees for 12 hours before. Turned out amazing.
Good post, you are Correct...Sort Of...
Yes, the USDA recommends Hot Food be held 140+. But, that is Hot food that will be Exposed to Bacteria, like a pan of Pulled Pork on a Buffet, and by Regulations in Restaurants and Food Service operations with often poorly trained and less than conscientious workers.
Realistically, if you pull a 225°F Brisket out of the smoker and Immediately wrap it in Paper or Foil, cover that in Towels and place the whole deal in a Clean Cooler. It really does not matter how low the IT goes over the next 12 hours or so.
It would take some seriously Beefed up, Genetically Modified, Super Bacteria to get in to a Closed Cooler, passed a couple layers of Towels, through the Foil or Greasy Paper, on to the less than 140° " Salted " Brisket and then, multiple to any Dangerous Numbers!
Now if you or your family/guests open that cooler and start Picking at the meat, with Dirty Fingers, we are back to making sure the meat Stays above 140°F...JJ☺