Why aren't the filters during the rise of intelligent life and during intelligent life surviving long enough to settle the islands?

The entire point of the analogy, as far as I can tell, is to move to a domain where our intuition works better. We don't have strong intuition about time frames and probabilities involving the rise of intelligent life. We do have intuition about tribes exploring and colonizing islands. We don't have strong intuition about how long it takes for intelligent life to reach the point where they can settle islands. We do have intuition about the likelihood of natural disasters wiping out island tribes.

It's a matter of time scales and probabilities. Robin Hanson's filter involves astronomical time scales and difficult to measure probabilities. James presents an example with human time scales and probabilities that are relatively easy to measure. The point is not to capture the physical acts (colonizing the stars), but to capture the anthropic reasoning and conclusions.