Here's the link to the original blog post, for those that haven't read it yet. The author is just having fun doing language learning as a hobby. The blog is hosted on Substack, but they're not selling anything or claiming to be a language learning guru.
The author has significant prior experience, being at least bilingual (Russian and English), and having done doctoral and postdoctoral research on
Oji-Cree. Given such a background, attaining a basic command of a language's phonology and grammar in a month doesn't sound far fetched to me.
Cambridge English estimates that it takes an average of 180-200 guided learning hours to reach A2 in English. That's 6-7 hours of intensive language learning per day for a month. I would add 1-2 hours of less intense listening. For example, watching TV and movies, listening to podcasts and music, and spending time listening to native friends and family. That sounds sustainable, if done as a full-time job.
Even if I had the time, I wouldn't want to follow such a schedule for 12 different languages in a year. Maintaining the knowledge would be easy enough using an SRS, but I would rather focus on quality over quantity.
Anyway, the author isn't trying to rush to a certain level in each language, and they're not following a strict schedule or even tracking hours. They're literally just exploring, having fun, and writing about the experience.