I think the FDA with its nutritional label standardization rules, which specify the range that a “serving” should fall in, is to blame for this arbitrary distinction. Otherwise it would make sense to call the whole 16.9 ounce bottle one serving.
Yes, but he’s blathering about it here to try to make it sound like he’s got a lower-calorie product than he has. That’s how manufacturers use the serving designation—and they’re free to determine what their serving size should be.