In short, the authors of that section claim that it's not really possible for the SREs at Google to spend all their time solving novel problems through automation.
This makes sense: constantly solving new problems is hard. It takes lots of time, mental energy, and the outcome is inherently uncertain.
Google found that some amount of toil (roughly defined as repetitive tasks that are not particularly challenging and do not solve long term problems) is essential for the health of their engineers. Toil is boring yes, but can be relaxing, and as work that is inherently easier to accomplish, can help keep confidence that working on solving unknown problems can deplete.
I would have expected that Google would have absolutely minimal toil, given that they are leaders in the automation space, but if they've found that some amount of easier work is necessary, then it's probably true for anyone.