Author is saying that some decisions aren't as obvious as "my code should be reliable under high load". Some decisions are tradeoffs that require you to have domain/technical expertise to answer.
And some do require design thinking. Like sndio or alsa, drm, caddy, … With no domain expertise and technical knowledge, a lot of software are out of scope.
And some do require design thinking. Like sndio or alsa, drm, caddy, … With no domain expertise and technical knowledge, a lot of software are out of scope.