At some point the program goes a bit overboard. If you are in Yellowstone (high use area) I can see the efficacy of packing out your poo. In the middle of the Alaskan outback, I doubt two Lincoln Logs are going to give Smokey much heart burn if he tramples across them. The local indigenous folks have been doing it for millennia.
I've got just as much chance of passing on something inside me from urination, spitting or blowing my nose (air hanky) as I do from my own scat. It's all about minimizing our impact. IMHO, a few human scat holes properly covered won't do any more damage than our footprints or anything else we do in the wilderness.
This may get this thread tossed into I & P but I'll continue on anyway. Urination will leave a human scent, just like any other animal's unique scent. If done on a rock, or on a tree, there's nothing they can "dig up" and thus they won't mess with the ground. They will just sniff, and move on. Spitting and nose blowing isn't much of a human scent target, but bears, like pigs are scavengers and they will basically eat anything they can find, yes, and they will find and dig up what is left behind.
I had a dog that would regularly find "dog treats" in the cat pan. Grossed me out. I checked with my veterinarian about that and he said, a lot of lupine animals will find such practice in line as well. His solution to my problem pooch was to sprinkle the treats with cayenne pepper to discourage them. I don't know if that would work for a chihuahua or not.
So now we have bears, wolves, coyotes, feral pigs and such that will find the treats and dig them up, leaving quite a mess in that area. Most of these are pack/herd animals and will draw in more than just a single bear.
All these principles of scent also apply to food scents as well and soaps and other fragrant items left over from washing.
The whole idea of this whole process is to not make a target of oneself, or worse yet, the next human in the area that is unaware of the target on their back and gets a nocturnal visitor checking out the scents.
Most places that have marked campsites usually have a firepit and drop box toilet for each site. BWCA and Philmont both do in the primitive setting. That simplifies the LNT problems, but in more remote areas of heavy human traffic along trails, that will offer up the wildlife quite a nice banquet table that could extend for miles.