I'm not talking about a dissolve. Having recreated a few of the crawls myself, I know that the Star Wars logo, the starfield plate, and the crawl text are all separate elements. What they did was either take the logo element or the text element and change their timing so that they were onscreen at the same time. Either the logo was delayed a couple seconds, or the text was moved up a couple seconds. And of course they sped things up as well for effect in the trailer.