Transmission fluid likes to be at a constant temperature. If it is too hot or too cold for too long, the performance can fluctuate and potentially cause damage to the transmission.
If the fluid is at a constant temperature, it behaves in a consistent manner in terms of its friction and lubrication properties. What can help control the temperature is the transmission cooling circuit.
The path of the fluid in the transmission lines is not as much about the destination as the journey. The size and length of the transmission lines, along with the size of the cooler, controls the temperature of the fluid. Also, the size of the engine and weight of the vehicle can determine the design of the transmission fluid cooling circuit.
Another thing to consider is how a modified transmission with a larger transmission cooling circuit might do more damage than good. On modern vehicles, the cooling circuit is designed to manage the fluid temperatures during startup. If the fluid can’t warm up quickly due to the increased volume, damage to the transmission friction surfaces can occur. The same goes for a bypassed cooling circuit. Why? Because fluid that is too hot can damage friction surfaces.