The author has a slightly funny use of the word engineering. If you look at its use in a conventional field like making cars then the science bit is the basic physics and chemistry of how gasses expand etc, the engineering is designing the machinery so the brakes work, the engine produces enough power and doesn't break and the like and then human issues like whether the workers go on strike or the end users are idiots and crash are not engineering.

Similarly I'd say in software the engineering bit is making reliable systems that are fault tolerant and secure and so on and then the people bits like the user interface are something like design and psychology, not engineering.