I read somewhere -- possibly an interview with Burtt -- that they used the 70mm mix for the latest version of Empire. They considered the 35mm mix "canonical," but used the 70mm as it was a better source. Whatever. And then they just "didn't notice" the line change until some fan pointed it out to them.

Of course, that's there usual tack of evasion. Either it's a "deliberate creative decision" or "we didn't notice it -- therefore, it doesn't matter, and you're a real dweeb for thinking that it does."

(I know there's other differences between the 35mm and 70mm mixes, so this could all be wrong.)