I think you did misunderstand him.

If the root fs is filled and the phone basically won't boot because root is full and the battery has run down so you can't charge the battery.

So you have two problems, the root is full, you need to clear out so me of root so the OS will run, but you can't boot because maybe you had just bad luck and have a run down batt at the same time.

This is a problem, because having a process go rogue on you and fill up /var with a zillion messages happens. This fills up root and locks the file system. If this happens while you're snoozing and your batt runs down, ohh well...

If this can happen, I would put this in the "Real Bad" category.

That's how I interpreted "Bricked". It's been mentioned that if you fill root, your phone gets bricked.