I’ve always shifted into neutral when waiting at a stop-light on my automatic equipped truck. I don’t like the idea of having to hold the truck back with the brake pedal, you got the engine fighting with the brakes, when shifting to N is so easy to stop the ongoing battle. Whether it helps or hurts the drivetrain and brakes, probably doesn’t make any notable difference either way. But shifting to N it is easier on my lazy leg and foot.
I wouldn’t shift into P however. From D you have to shift through N and R to get to P. And it would be easy to accidentally shift into R instead of P, and accidentally back into the car behind you. Plus shifting in N still usually requires a little brake pedal to prevent rolling, which keeps the brake lights on, just as it would with a manual trans. Shifting from D to N is just one click, very easy.