Have _you_ timed it? Not in general, but for this specific case? Thread creation is relatively expensive to some operations, but maybe the speed is entirely irrelevant to the task at hand. In this case, the author of the article is auto-curating some articles from a list of people he finds interesting. If this were done once per day as a cron job, it could almost certainly be done entirely _serially_ with zero concurrency and full blocking and still finish fine. Adding in concurrency is nice, but certainly any method will do with this volume.
This is certainly one of the cases where you should just do whatever is simplest (to _you_ the programmer). The first step is always to optimize for cognitive overhead. I.e. make the code easy to reason about. Next (and relatively rarely) is it necessary to good to optimize for different bottlenecks in your code.