As many have commented herein, the 8spd transmission in the 1500's gets hot, and it's also a known issue that the thermostat valve can stick and cause catastrophic damage to the transmission, and for one of a better term, wipe it out.
Regardless, as we all know, heat is the #1 killer of any transmission.
So, being a car guy and very in tune with my vehicle and being able to feel how it runs in all terms of the sense, I knew that my transmission oil was getting worn. With the help of the brain trust on this forum I was fortunate enough to be directed to the designer of this mod/upgrade, and I actioned its installation combined with a coolant flush and fill and new thermostat (done in conjunction with my major 100K service).
Everything to do with our vehicles is a tad more unique than other OEM's in terms of our engines and transmissions run a bit hotter than most, and we have to contend with a lot more proprietary nonsense too when tuning and upgrading audio and lights, etc.
That said, you're correct that fluids do have an optimal operating temperature range. But being able to reduce the operating range by say 25 to 30 deg/cel at full operating temperature in this transmission specifically is a huge bonus and it is immediate in its deliverable of extending the 8spd transmission life cycle and overall operating efficiency, too.
The reduction is transmission temperature with this mod has been proven to be of significant and quantifiable benefit by those who have installed in in their daily's and high HP vehicles, and it has had no detrimental short or long term effects either. Trucks in the patch have more "air time" then they do "drive time"
I live in Ontario, Canada and with this mod installed I have gone from +40 to -40 deg/cel outside temps and my transmission is very happy and works flawlessly. However, no matter the outside conditions, I always allow my vehicle to reach its prime operating temperatures (oil, coolant, transmission) before I go and drive it in any type of spirited manner, because flogging a vehicle from stone cold could cause stresses that could have negative impacts. In my opinion only, it's always best to let your vehicle get to prime operating temps first.