I see what you mean... when the record light is armed on the main bus it just means that SOME track SOMEWHERE is armed to record.
While that might not seem like a big deal, with a high track count (where you can't see some of the tracks on screen) it can be a lifesaver.
The Mute and Solo buttons above that will also light up just to let you know that SOME track somewhere is muted or solo-ed.
I'm surprised that you can turn it on or off manually, to be honest. I'd never tried but on older consoles you can't change it's state - it's just a light usually, not a button.