If you emphasize reading and listening, then what you can understand when reading and listening will increase more quickly than what you can write and speak. On the other hand, if you emphasize writing and speaking, then what you can write and speak will increase more quickly than what you can understand when reading and listening. This can be summed up in the following chart:
Looking at this chart, it's easy to see how you can only expand your writing and speaking as far as your ability to understand when reading and listening. As your writing and speaking approaches the limits of what you can understand when reading and listening, you need to expand what you understand when reading and listening. Otherwise, your writing and speaking will stagnate.
This, however, hardly means that you should focus on reading and listening while pushing off writing and speaking to some amorphous point in the future.
That is pretty close to Steve Kaufmann's approach. At the outset, he focuses almost solely on reading and listening, causing the outer circle to expand quickly, while basically ignoring the inner circle. That doesn't mean the inner circle will be stagnant; indeed, by coming to understand more when reading and listening, the inner circle will expand—but slowly. Steve is patient enough to wait for that circle to expand enough until he feels "ready" to speak.
This contrasts to an approach, which I believe is shared by Benny the Irish Polyglot, Randy of Fluent Every Year, and myself (correct me if I'm wrong, guys), in which writing and speaking get attention early and often; there's no waiting until you're "ready" (i.e., waiting until that inner circle gets big enough while you slowly convert language you understand passively to language you can use actively). We all push that inner circle to grow from early in our language learning.
Language learners will need to constantly make a choice between whether to allocate time to readling/listening and writing/speaking. In the early stages of a language, Steve is at one extreme, focusing almost solely on reading/listening. Unsurprisingly, this will cause the development of reading/listening skills while writing/speaking skills lag (the outer circle grows quickly, the inner grows slowly). If you go to the other extreme and focus on writing/speaking, the inner circle will quickly catch up to the outer circle and you'll be stuck with no where to progress in your writing and speaking.
So the trick here is striking a balance in the middle ground so that both circles expand together. I would still say that the majority of your time at the outset is going to be spent on reading/listening, but a healthy chunk of your time should also be geared towards writing/speaking. In my experience, this way has always led to me being able to quickly communicate with people, without needing to wait for some "ready" moment somewhere down the line.