The article is meant to be taken as a general guide. The author does suggest that we use a pre-programmed crawler rather than code one ourselves. Refer to this passage:
"Crawler. If you don't use an open source crawler, my advice is a super-simple multistep crawler. This is very important advice that will cut months off your development time, so if you ignore everything else, don't ignore this."
"Crawler. If you don't use an open source crawler, my advice is a super-simple multistep crawler. This is very important advice that will cut months off your development time, so if you ignore everything else, don't ignore this."