[chamilto]

> If web developers don't already all know this then what knowledge do they have nowadays?

Read the article's title. This article is clearly aimed at people who are starting to learn web development. It is not aimed at experienced web developers.

> ...these were all skills I had mastered before even attempting to define what type of development I wanted to do

Many people learn how to program by working on projects they want to work on, and a lot of people want to build web applications.