But if a child is consuming milk instead of water of course it will make them gain extra weight. 8oz of water has 0kcals and 0g of fat but 8oz of full fat cows milk has 149kcals and 7.7g of fat. If a child is having a full diet they don't need milk in such large quantities.
Quoted from the article:-
?A 24-month-old girl of average weight and height who is put to bed with an 8-ounce bottle of whole milk would receive approximately 12% of her daily caloric needs from that bottle,? said co-author Rachel Gooze.
That's quite a bit extra on top of the food they would be eating - after 8 days thats an extra days food 
I'm actually trying to stop my 5y/o from drinking milk now as she has adult teeth so is beyond needing milk (from whatever species) as she gets enough dairy through yogurt/cheese. Her serving size is around 2-3oz now unless it is given instead of part of a meal.
Full disclosure - I bf into toddlerhood/childhood but I treat a bf as a meal/snack not as a unless it is a quick comfort nurse. It's part of their diet not a add on.