What it doesn't include is all the higher-value work the people on the Operational side tend to provide, like thinking about rollbacks, machine failure, network failure, provisioning, capacity planning, change/configuration management, security, monitoring etc - which is not to say that all developers don't think about these things, their focus tends to be on developing product rather than these non-functional requirements.
I'm presently in a world of Ubuntu LTS+a few manual backports for similar reasons as the authors. My home systems are ansible managed, giving me things like wireshark installed everywhere if I need it and new machines automatically hooked into Prometheus monitoring (which is much easier with my debs). I've seen what happens if you try to manually manage machines, and know that a small bit of upfront work will bring dividends later.
Writing the core code is just one critical step in running software long term, let's not forget the rest of the critical steps to keep it running in a sane way in the future.