How weird, so it's different in other ways, too? Here's my theory:
We know from Stevie's changing outfits on the video (and Lindsey's disappearing underwear line) that there were two shows edited together for the Mirage video. I don't think they worked on the vocals, just took the best of the two. The reason I don't think they reworked the vocals is because Lindsey's voice strains a couple of times and they didn't clean that up. The Chain and Go Your Own Way are two examples of that. Oddly enough, despite that fact, those are two of my favorite songs on the tape! lol
Unfortunately, this is only a guess. Anybody a little more knowledgable got an idea?