Some sites are very complex to move, so any additional help and assistance to ensure consistency in the SERPs is of value, imho.
Few topics confuse and scare webmasters more than site moves. To help you avoid surprises, we've created an in-depth guide on how to handle site moves in a Googlebot-friendly way. So what, exactly, is a site move and how do you go about moving a site correctly? Basics of site moves A site move is, broadly, one of two types of content migrations:
Site moves without URL changes. Only the underlying infrastructure serving the website is changed without any visible changes to the URL structure. For example, you might move www.example.com to a different hosting provider while keeping the same URLs and site structure on www.example.com. Site moves with URL changes. Here, the URLs on the website change in any number of ways: The protocol: http://www.example.com to https://www.example.com The domain name: example.com to example.net The URL paths: http://example.com/page.php?id=1 to http://example.com/widget Google Publishes an Updated Guide To Site Moves [googlewebmastercentral.blogspot.com]
It may be a result of interpreting 302's as showing the mobile or desktop (depending on which way its going) version of the same page, which is presumably why they recommend 302s for separate mobile sites.