So they don't mean there are specific things that are incorrect in MLton - there may not be any examples anyone can give you - they mean that we don't know mathematically how correct MLton is or not, because nobody has done that work, and we do know to a better extent mathematically that CakeML is correct, because it has been mathematically proven to be correct to a certain degree.
So they don't mean there are specific things that are incorrect in MLton - there may not be any examples anyone can give you - they mean that we don't know mathematically how correct MLton is or not, because nobody has done that work, and we do know to a better extent mathematically that CakeML is correct, because it has been mathematically proven to be correct to a certain degree.