Google Base S2 added to robots.txt

Google just added a new disallow entry into their robots.txt file: "Disallow: /base/s2".  This comes after talk that Google will be focusing on product searches before the end of the year.
Could "s2" be "search2" -- the second generation of Google Base searching?  Right now, visiting http://www.google.com/base/s2 gives us a server error stating: "The server encountered a temporary error and could not complete your request.  Please try again in 30 seconds."

Update:
An interesting discovery made by a reader of the blog -- going to http://www.google.com/base/s3 (or anything after /base/ for that matter) will give you an error message.  By looking at the source code for that error message, Nick finds an internal URL probably used for testing or development purposes: http://jck27.prod.google.com:9828/base/