Yeah, I think it's a nice solution but it only works in very narrow circumstances.
Once I was given a much smaller, unpaid task as part of the interview process. It wasn't a puzzle or trick, but something actually useful. All told it took me a couple of hours one evening. You might be thinking, "How much can you learn about someone from such a small task?" It depends on the task, of course. Mine was typical network code, with a couple of non-obvious but absolutely real-world edge cases. I spent time making sure my comments were great, and then wrote a man page. I think they learned some important things about me, and on my end it was an easily paid investment.
We've been using something like this but centered around concurrency rather than networking. It works out great, you get to compare across many candidates how they handle the tricky parts, if they understand the standard vocabulary of concurrency, what their coding style is like and if they understand basic C++.
One thing we noticed was that there is small handful of mistakes that many candidates tend to make. The ones that note the existence of a mistake or work around them skillfully are typically the best.
Yeah, something small is probably okay. I know that I've invested more than that preparing to interview for a new job (brushing up rusty skills, revising algorithms I don't use but interviewers love to ask about). The author talked about hiring people for weeks. I think that is too long.
Once I was given a much smaller, unpaid task as part of the interview process. It wasn't a puzzle or trick, but something actually useful. All told it took me a couple of hours one evening. You might be thinking, "How much can you learn about someone from such a small task?" It depends on the task, of course. Mine was typical network code, with a couple of non-obvious but absolutely real-world edge cases. I spent time making sure my comments were great, and then wrote a man page. I think they learned some important things about me, and on my end it was an easily paid investment.