2kg in 2 days doesn't sound unreasonable at all. Glycogen and water loss from the calorie restriction will do that, along with maybe better bowel regularity from the fiber. Nobody is claiming they lost 2kg of body fat.
Sampling an implicit function on a grid shifts you to the world of voxel processing, which has its own strengths and weaknesses. Further processing is lossy (like with raster image processing), storage requirements go up, recovering sharp edges is harder...
As a non American some of these numbers are just mind boggling. Only putting the warning on drinks with more than 50g of added sugar, a 'medium' Dr Pepper with 67g of sugar and a large with 96g.
I don't think they do, people move around and swap seats. I expect they just find the losses small enough to write off. I was once travelling shortly after being issued a new debit card, but still had the old one in my wallet and used it by mistake and I wasn't charged. They never tracked me down for the cost of that packet of crisps!