So many words are interchangeable - the logic your firend presents makes perfect sense. Many people get caught up in the 'stay' instruction versus the 'wait' instruction, when they are actually identical. The dog stays in one place until they are released, whether that is for 2 seconds or 2 hours.
We don't get caught up in having a dog forcibly sit the entire time. In fact, if he wants to lay down why not let him be comfortable? It just means that he has fully committed to hanging out until told otherwise.
But we aren't anal about the things that would put a competition obedience trainer over the edge. We just want a great dog whose is wonderful to live with.