When your dog is looking at you while it's pooping it's likely saying that he or she wishes you would look away because they're wanting privacy and don't like being stared at while doing their business.
It can also be that they're just on more of an alert in case something tries to attack them so they keep watching you to see if you alert them to something.
I've always just looked away until my dog poops because I like my privacy as well so I just show the same courtesy to my dog even though it's likely not needed.