That isn't the only problem. Small or not, it's a needless waste of space on a tablet screen to create a separate system bar from the button bar. It's not big, but it's more than a few pixels too.
The other problem is now you have the 3 big buttons in the middle of the screen, not as easy to reach, pressing the spacebar on the onscreen board results in frequent accidental hits of those now centered buttons.
It's like someone at Google checked their brain at the door when they decided to put this on a tablet. They preach to app developers to make their apps more tablet optimized then do the exact opposite with Jelly Bean. Haha.
And a lot of apps don't hide the buttons or notification bar like I'd like. Chrome browser is a big one.