IIRC their original hardware plan was based around commodity hardware and getting the most performance per dollar since they built the crawler to be distributed pretty early on.
Point being, consumer grade hardware has come a long way since then, and if you're doing something cutting edge like DL it's not outlandish to expect that rolling your own might be worthwhile and totally justified.
Google's start up between 1996 and 1998 was also over twenty years ago. There were fewer than 200 million Internet users on the Internet and less than 2.5 million web sites [0] in 1998. Google was also started by two college grad students, meaning gasp it was initially just a research project. I'd also point out that while, yes, the initial production servers were cheap and used commodity hardware, this [1] is what they looked like, which is hardly the type of setup that the article is suggesting.
[0]: http://www.internetlivestats.com/total-number-of-websites/
[1]: https://en.wikipedia.org/wiki/History_of_Google#/media/File:...