There's certainly truth in this notion - if you have a goal in mind, going directly after it is often the most effective and straightforward choice. What I'm advocating is that the most direct path isn't always obvious.

Many masters say the fastest progress can be made in chess by doing "find the checkmate" exercises on tricky or otherwise interesting positions. This aspect of chess disproportionately contributes to success, compared to how much time is spent on each of these positions in the natural course of play. A bit of meta-knowledge about what makes someone successful at chess lets players play more effectively by focusing most on whatever helps them win.

Similarly, if you're learning a language and find yourself constantly groping for the right word, you might make a connection between your ineffectiveness at communication and lack of a memorized vocabulary, then shore it up by focusing specifically on that.

While there's a very strong correlation, there's no special rule of nature dictating that the best way to learn a thing is the same as doing it.