The Ubuntu Touch image model has been flipped around so that Android is no longer on the bottom side and that Ubuntu is going for a different position.
Oliver Grawert wrote a mailing list post
in sharing that these new "flipped images" are now the default for Ubuntu Touch.
What do these flipped images mean? "The legacy Ubuntu Touch images run Ubuntu inside a chroot on top of android. For the flipped model we are instead booting directly into Ubuntu and then start up android inside an LXC container before starting any services/applications. Currently we're providing images for maguro, mako, manta and grouper, and all are tested and known to work."
Basically, with Ubuntu Touch relying upon Android, up to now Ubuntu Touch would be booting Android (CyanogenMod) and then from there launch Ubuntu from a chroot. Now instead, Ubuntu Linux itself is booting on the hardware and then starting up Android/CyanogenMod within an LinuX Container (LXC).