While I agree with your advice in the general case, I also find the author's data point interesting and compelling. Receiving 2 offers from 7 interviews with only 16 applications is a good rate in software engineering as far as I am aware.
It's also worth pointing out that the cover letter mentioning "rare programmer" ultimately led to an interview and an offer according to the author.
It depends. For the types of companies he was applying to - yes.
For your standard experienced “enterprise dev” in most major US cities outside of the west coast and NYC, pre-Covid the demand was so high and so few experience developers come on the market, you could usually find a job in less than a month depending on if you were looking for the “right job” or the “right now” job. That’s been my experience since 2000 with the exception of the years between 2008-2010.
Of course that’s if you do enough resume driven development and have a strong network of former coworkers and local recruiters.
It's also worth pointing out that the cover letter mentioning "rare programmer" ultimately led to an interview and an offer according to the author.