Pierre Far, Google's Webmaster Trends Analysts and co-author of the blog post with Zineb Ait Bahajji wrote on Google+ that this is a massive rewrite of the documentation.
He said that from his own experience working with webmasters, there are "few topics confuse and scare webmasters more than site moves." So they've "massively updated" their help documentation about planning and implementing the best site move possible.
You can read the new and updated site move guidelines online.
The documentation is broken down into two categories:
(1) Site moves without URL changes
(2) Site moves with URL changes
It also discusses handling mobile sites.
Forum discussion at Google+.