I figured the plan comes from how human intelligence seems to be built up in two stages, first the genetics-driven fetal brain formation without significant any significant sensory input to drive things, then the long slog of picking up patterns from loads and loads of noisy sensory data from toddlerhood onward.
Working from this guess, anatomical differences between the brain of a toddler and the brain of an adult aren't important here, the point is that after the "toddler" stage, a human-inspired AI design will learn the stuff it needs by processing sensory input, not necessarily with additional brain structure engineering.
There may be a case to be made why such a human-inspired design is not the way to go, but you seem to be arguing against an AI that's designed to stay at the level of a toddler, instead of proceeding to learn from what it observes to develop towards adult intelligence like real toddlers do.
Why should it take an AI design more than five minutes to process a significant enough amount of rich sensory data to push it to an adult level?
Upon review, I think you are correct that this plan does think it's solving all the major programming problems by the toddler stage, and the rest is just education.
But the question is still: If you understand how to make intelligence, why make one that's even nearly as low as us?
http://multiverseaccordingtoben.blogspot.com/2010/10/what-would-it-take-to-move-rapidly.html