Not sure which example you're referring to, but all the "all you can eat" restaurants I've been to always respected their promise, as in, you literally can eat

Not sure which example you're referring to, but all the "all you can eat" restaurants I've been to always respected their promise, as in, you literally can eat as much as you can. I was never charged more because they decided I was full. Certain restaurants have a "no food waste" policy that will make you pay the stuff that you don't eat.