I don't work as an SRE, but isn't that covered by providing engineers physical access to secure facilities in the absolute worst case?

The article states:

> The defense in depth philosophy means we have robust backup plans for handling failure of such tools, but use of these backup plans (including engineers travelling to secure facilities designed to withstand the most catastrophic failures, and a reduction in priority of less critical network traffic classes to reduce congestion) added to the time spent debugging.