I don't think they so much released chapter 8 as made it available under certain circumstances to people, who, of course, then spilled it on the internet. As for releasing chapter two as an audiobook, this is exactly what they did with tGS last year. First chapter one, than the audio chapter two. They released the two to promote two different formats of the book, rather than having two versions of chapter 1 and people ignoring the format in which they were uninterested. At least, in theory, people will pay attention to both previewed formats now, but once again, their intentions count for little next to the internet, where a transcription can pop up right away.