I have noticed on occasion,at some full hook-up camp sites that when the neighbors (sometimes) drain their tanks, or when leaving the campground, the "poop" odor is awful in the air. Now everyone agrees their own "poop" does not stink, so this does not apply to YOU. It applies to the camper parked beside you .... right?....
Anyway, I think if the black tank contents are spilled on the ground, it stinks everything up, and yes, those odors will penetrate inside the camper.
I think if you neighbor does not use any kind of deodorizer and make any attempt to keep their tanks clean by something as simple as flushing or back-flushing, when dumping, the smells will escape from the campground dump spot (hole) and fill the surrounding air.
If they have any kind of leakage in their sewer hoses, smells get in the air pretty fast. If they disconnect their hoses without properly flushing first, the smells in the hoses and at their black and gray water outlet valves will put odor in the air. All of this will penetrate to inside the camper, not to mention their next door neighbor (you and me).
Bottom line is, they should not have odors, coming inside the camper at all if they would occasionally simply flush and rinse out their tanks real good. Something as simple as pouring a bit of Dishwashing liquid in the toilet goes a long way to help clean their tanks out too.
So the next time you wake up on a Sunday morning and your neighbor is breaking camp and you DO NOT smell roses, you might give him my advise!
And oh ... contrary to popular opinion, gray tanks can, and "do" smell sometimes (there again ... only your neighbors). Their cure is simple. They need to fill the tank with clean water and simply drive around a little then dump. It will wash their gray tank and odors will be gone. No need for additional soaps or anything. Clean water will wash out the gray tank. (If only your neighbor campers would read RV.net... right?)