The same applies to learning languages.

You can learn a lot from textbooks... or you can use textbooks to give you the absolute bare minimum, and then just use the language itself repeatedly.

I think the idea is very deep and applicable to many aspects of life.

Learning grammar, vocabulary, semantics, etc. is definitely valuable. But immersing yourself in a culture where the language is spoken, listening how it is used in practice, speaking it yourself with a native, that is a truly powerful way to learn the language.

I'm not religious but I am reminded about a story where Jesus was challenged about his disciples picking some wheat on the Sabbath, breaking a law. The Pharisees demand an answer and Jesus says that the Sabbath was made for man, not man for the Sabbath. He was pointing out the inverted relationship and the corruption that results.

The same can happen with music, programming, language learning, etc.

Another analogy most people will recognize: the map vs. the territory. Music theory is the map, the songs are the territory. No matter how much you study the map you will benefit tremendously from walking the territory.