OH. Wow, since they aren't visually differentiated from the other arrows in the tab well, I assumed they were there to as another way to scroll left and right in the tab well.
Feature request: Get the navigation buttons out of the tab well. No other application I've ever seen does it that way.
Alternative: Make them visually different than other buttons in the tab well so they don't "blend in" and are obviously not for tab well manipulation.