Natural languages depend on redundancy. It's why "Coca-Cola" becomes "Bite the wax tadpole" when you try to limit yourself to three or four sound groups.
Among a common group sometimes the redundancy is not the words used, but the phrases have a meaning to the group beyond the words.
For an AI to accept natural language would require it to be intelligent enough to consider all outcomes of its' actions and choose the most reasonable one. Asking where unsure.