I've seen videos of the process too. They didn't discuss maggots, so I don't think flies can get at the meat under even the rocks much less the dirt, and I'm guessing it's not an issue with the oil in the shark stomachs because the flies can't get at the oil, but it might be unappealing to people to have flies on the stomachs, though I don't see any in the photo.
We should probably have a sticky thread to put all the high meat videos into--those of the Inuit, Chukchi, Aajonus, etc.