If I sit down for dinner at an all-you-can-eat buffet, I get to decide how much I’m having for dinner. I don’t mind if they don’t let me take leftovers, as it is already understood that they mean as much as I can eat in one sitting.
If they don’t want folks to take advantage of an advertised offer, then they should change their sales pitch. It’s explicitly not gaming any system to use what you’re paying for in full. That’s your right and privilege as that’s the bill of goods you bought and were sold.