Ubuntu Policy Manual - I just started reading the https://wiki.ubuntu.com/UbuntuArchitecture which outlines the overall architecture of Ubuntu. Got to the section that discusses the Ubuntu Policy Manual and that it is derived from the Debian Policy Manual, which I think is great. I then noticed that at the bottom of the Ubuntu Policy Manual page and noticed that the document has not been changed since 2009-06-19. I then went and took a look at the Debian Policy Manual and noticed it was just updated on 2011-04-07.
Could be that no changes have been necessary, but given the tight symbiosis between Ubuntu and Debian I would think that there would have been a more recent change date for the Ubuntu Policy Manual. It could be that the Ubuntu Core Developers have just not had a reason to updated the document in over two years, but just looking to better understand why.