When I am driving a modern computer controlled vehicle such as your Jeep I presume the manufacturer's engineers who set the transmission shift points knew what they were doing. I don't second guess 'em. I let the transmission do what it was programmed to do.
The vehicle computer senses the load on the vehicle and shifts the transmission accordingly. If you manually shift too soon you might get the engine RPM's too low for the combination of load and throttle position. That could lug the engine thereby putting more stress on it.
See this ARTICLE
for an explanation of lugging an engine.