For one thing, to get a brain thinking, there's a whole lot of the brain you don't need. You don't need heartbeat and breathing regulation; you don't need vision, hearing, touch, etc.; you don't need blood vessels, you don't need carefully constructed layers of fluids...
But, if you want to simulate a human brain, then you do need all those things.
It's another version of the reductionist illusion that the original article rails against. The myth of the duality. Instead of the mind/body classic duality, we get the neuron/infrastructure duality. Or, in the original article, the fiction of the separation of DNA and its expressive machinery, as if DNA was code, and the biological machinery was a fully separate computer when the DNA has evolved in coexistence with all its machinery - and its expression. In simpler words, do not forget that it's probably commonly the case that DNA has evolved to "express this protein" not because "this protein does X" but because this protein happens to trigger this event at this point of the organism life.
Think about it for about a second. If the blood vessels and all that aren't necessary, then why would the brain function be affected by things that happen there. There's a simple experience you can do that will show you that your brain is affected by blood chemistry: Get a stiff one or a dozen! The obvious imbalance in the way brain functions (from reaction times to higher-level inhibition lifting) introduced by alcohol suffice to dismiss the idea that neurons work in splendid isolation, being only affected by neural input. Your entire brain is affected by your body, in myriad ways, and not just sensory ones.
If you're not simulating a human brain, you can get away with those things. If you're simulating a kind-of-brain, it might work in abstraction. If you're trying to make strong AI, you might even get away without even simulating a single neuron. But simulating the real thing? Dismissing all inputs except sensory ones is probably a premise that's unlikely to turn out true...