The "fully grammatical" approach towards learning Indo-European languages

Question

I have stumbled upon this video on Youtube (sorry - it is in Russian).

Here's a short summary:

The spokesperson introduces the following scheme of learning an Indo-European language:

1. "Learn by heart" a book which describes the language's grammar without any exercises, and restrain from approaching any other materials (thus, concentrate on syntax and morphology).
2. Read a book without consulting the dictionary.
3. Read another book consulting the dictionary not more often than thrice a page.

The spokesperson claims that the Indo-European languages follow some patterns which make this approach possible.

Truth be told, I reckon syntactical and morphological to be an imperative part of learning a new language, yet I've never tried concentrating on those points that much.

1. Has anyone tried learning a language following this or some similar scheme?
2. Which patterns could have the spokesperson been hinting at?

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Edit:

The spokesperson does not specify whether this is exclusively about learning to read the language or also about using it actively. People in the comments referenced a similar method (the video is once again in Russian, sorry) which is meant for reading according to the author. Others also backed up the "passive" nature of the acquired knowledge and skills.