My guess is that no one knows. But the lack of rotation support was a major complaint by users around here for a long time. Given how delightful the tablet is in portrait mode, especially when spoofing an iphone's user agent, I'd say we'd better just count our lucky stars that we are able to implement it ourselves fairly easily.

BTW, for those who don't know about the iphone spoof trick and want to try it, enter the following into the address bar of your browser and wait for it to process:

To unspoof, enter this:

With spoof enabled, sites like gmail, http://www.google.com/reader/i , and Powerset (wikipedia) work like a dream.

ADDING...: Once your browser has processed the command, go to "Add Bookmark" and add "iphone spoof" and "iphone unspoof" (or whatever), respectively, and then you'll be able to switch back and forth when you want.