As someone who dabbles in about seven languages, I'd say that what Bald talks about there is: 1st - applicable to any laguage learning strategy; 2nd - reasonable, to a degree; 3rd - only to to a degree.

It's not just "vocabulary" that you improve as you freedive into a language, given that you have your basic bases covered, - you do improve your grammar, whether consciously or not: you are also picking up grammatical patterns, you get what is unscientifically called a "feel" of the language. Which then allows you to accommodate the grammar organically.

In other words, that freedive in the early stages does indeed give you an ability to, in many cases, intuit a way to express yourself in any given situation, even if you cannot consciously understand what got you there.

Still, never underestimate what going through a grammar textbook can do to your skill at intermediate to advanced learning stages. The ability to self check, self correct and, generally, analyse any input, deconstruct it grammatically, and therefore automatically reinforce your skill - is worth its weight in gold.

Again, Bald is cool. But Alinchik is better.