Thanks for sharing this, just bought the book based on this. I think I agree with this quote. I would also say (without knowing the surrounding context) that unplanned work / rework can also indicate structural/organizational issues.
IME, unplanned work can happen in an organization that is not set up to handle a sufficient amount of planned work / lacks coherent strategy / doesn't communicate that strategy well. Fire drills and "new" work often occur. This can just be because it takes time for information to propogate through the organization. Or because people at the edges doing the work don't have a clear priority (doing what is visible or for the squeakiest wheel, not what is ultimately most important). Even assuming no other dysfunction, if you are way over capacity on product/engineering (insufficient people/resources, requirements expire quickly) at some point you just churn due to organizational entropy. By the time you have figured out what to do, it has changed (rework).
(It probably depends on the scope of "quality". My guess is they meant overall quality (fitness for business), not just engineering quality.)