In Oracles on the Delphi Express, a prophecy given to The Boy, there's a line that goes "Big steam ships, exits illustrate the flaw". In the final song of the album, Vital Vessals Vindicate, there's a line that goes "Ebb to the left, flow to the right, the exit's unflawed".

I still don't understand what's meant by it. I think maybe it is about The Boy leaving? But then why the difference between "the flaw" in the prophecy and "unflawed" in the final song?