I have a manual slider. The auto that your talking about from what i have read somehow senses a turn and starts to slide. It has a gear mechanism in it and a special plate that goes on the pin box and automatically slides back and forth as needed. Somebody else may chime in and give you a better understanding of it.
I had a Ford F350 before with the resse manual and only had to slide it once because it was a tight spot. I havent had to slide it in my new mega cab yet. I know their will be times that it is needed but i just watch on turns and backing in and I have been fine. I also have a backrack on my truck and have to issues.
2008 Rockwood 8281ss
2006 Dodge Ram Mega Cab Hemi
Reese 15k Slider