Google knew they were trashing the Honeycomb-style tablet interface altogether, so they totally mailed it in with the Xoom updates. 4.1.2 doesn't include the ability to expand notifications with one finger like you can on the NS, N7, and Gnex...there's no JB wallpapers in the honeycomb-style tablet launcher, but if you change your screen DPI in build.prop to enable phablet mode, they're in there. They didn't include the Sound Search widget like they did on the NS, N7, and Gnex, they used the ICS boot animation as well. Google totally mailed in the Xoom Jelly Bean update. Period. And who could blame them? They knew it wasn't going to be a feature device for very much longer, its sales were dismal, and they were completely redoing 10" tablet mode.
A quick note on the boot animation...I understand that Jelly Bean's stock boot animation is a multi-colored X representing the Nexus branding, and it would't make since to include that on the Xoom. That said, however, there WAS an alternate boot animation. The special edition N7s that were given away at I/O 2012 (the ones with white backs) originally shipped with an early Jelly Bean build, version 4.1, build JFN53N. JFN53N shipped with an alternate boot animation that resembles one of the Jelly Bean wallpapers. Those N7s got an OTA right out of the box to JRN84D, which is where that multi-colored X made its debut as the boot animation. You can find the alternate animation if you look around. They could very easily have included that boot animation for the Xoom since it was branding independent.
Here's what the original boot animation looked like on an original Nexus 7 with Jelly Bean JFN53N. This would have looked awesome on the Xoom!
http://www.youtube.com/watch?v=LgEI5V8lcts