As someone who inadvertently tested this idea as a youngster, I can tell you that the indentation does pop out - all the way out, practically. A neat separation nearly 3/4 the way 'round, leaving a rather large hole for the milk to come gushing out of.
You have any idea how much floor area a gallon or so of milk can cover? :o
The store help, however, was very nice and let me get a new one, even though I’d already paid for this one and dropped it walking away from the cashiers. Whew!