The ATF is cooled just like your coolant by the radiator. The warming effect is great on cool winter mornings like here on the northeast when the truck will shift really hard until the ATF temp goes up. In Texas you don't have to worry about that
There was a huge class action lawsuit last year about it and Nissan extended the warranty to 100k for damage the radiators cause. I didn't want my truck to go through the problem so took action. When I asked my dealer about the bypass he said absolutely not, replacement is the only recommendation.
The second cooler in front is a supplemental ATF cooler which comes with the tow package. If you tow and don't have one that is essential. I always added a B&M cooler to any TV I had without a sup trans oil cooler. Yes it helps cool the fluid but is to be used in conjunction with the radiator.