The difference is you can't make one of the cans disappear during packaging and handling. Fact is that those people don't care that their sandwich is 11 1/2" inches, except insofar as its potential use as a vehicle for lawsuit.
If they cared beyond any monetary gains they stand to make, I would support them as far as I can empathize with someone getting pissed over a slightly deformed sandwich. But all they care about is the money and the attention, which puts them in a position of moral inferiority, even if subway was intentionally shortening their sandwiches (I am convinced this is not nessicarally the case).
Beyond that, isn't the point of the foot long just to be a large sandwich? The dough-ball almost certainly was weighed or otherwise measured (they aren't stupid human error can work both ways, potentially costing them money), which means what's 'missing' in length is present either in width, height, or slightly denser areas of the loaf (likely the easily squished and compressed ends of the sandwich)