Concerning the study of religion, an approach for historical accuracy is irrelevant. Most creation myths/stories contain their own disclaimers. . . its a myth/story. However in context of the religion the story may be evaluated. It does not need to hold to outside standards, but rather internally to the context of the religion.
One example would be that what was said in your example was not Siddhartha, but the Buddha speaking. That the transcendent nature of the Buddha allowed him to express his nature and overcome the human limitations.
Another approach would be to examine the cultural significance of the reaction and make them a parable of the divine nature of Siddhartha. Many people point out that the 'seven days' of creation can be accepted into science by giving a god a 'cosmic' sense of time. By attaching meanings to these actions these legends are not meant to carry the numerical truth, but rather a higher truth or knowledge.
But the question "Did Siddhartha live?" is one of history. The question of "Did [Mythical Religious leader] do [Action]?" becomes very touchy, and are usually studied without asking if they existed, but rather how their existence influenced a religion.
But with religious figures and the stories of their lives, it is better to separate historical from religious purposes. So many people feel that adding a historical 'fact' to their beliefs will validate their beliefs. And yet most people wish to ignore everything we call fact starts from belief in a thing called fact.
Look into philosophy and religious studies to see how beliefs are handled and keep in mind your beliefs on science are beliefs. Just because you believe in your history and data, does not trump another beliefs no matter how far fetched they are. Nobody has 'proven' gravity, history or even reality. The more you know, the more you are aware of how little we know.