His example of a web crawler stinks. I can get behind the philosophy, but his specific web crawler example at a minimum needs to retry, respect robots.txt, and rate limit per domain. So no, xargs + curl is a dumb example.
The idea stays: you can jerry-rig a web crawler from pedestrian, readily available parts, and quickly test the idea for which you wanted to crawl the Web.
The point is that bash, xargs, wget, make, etc are well-understood, well-maintained tools. They are not even necessarily simple, but they likely contain very few unknown unknowns.