gear lube vs. tranny fluid

Years ago I had a automatic trans that shuttered in certain overdrive speed/load conditions. After finding it had the wrong fluid in it, I had to ask how the fluid could make a difference. I learned that the shutter was still there but I wouldn't feel it.
The molecules of modern fluids do cushion and absorb the feel and sound of moving parts. Do they reduce wear and/or extend part life ? Time will tell.