Myers isn't trying to argue that the million lines of code aren't there or aren't important. He's trying to argue that those million lines of code have to run on hardware which is poorly understood at best, and that trying to reverse-engineer the hardware is several orders of magnitude more difficult than trying to understand the original programming. The hardware components don't follow the law of superposition, either, so we can't just look at each element in isolation. The entire thing has to be understood.
Imagine going back to ancient Roman/Greek/Etruscan/&c times and handing them a ream of paper filled with the hexadecimal representation of an x86 application compiled for a Windows environment, and then showed them what it looked like when running. "Hey, look, now you can play videos and music!" Now imagine it was several orders of magnitude more difficult than that, and you're beginning to get the idea.
"If you could reproduce those 1 million lines and set them loose, allowing them to construct a human being..." The exact point he was making was that there's a lot of handwaved complexity in this statement, and that the abstraction "understand human being program, run code" is abstract to the point where it no longer accurately reflects the reality of the situation.
He's trying to argue that those million lines of code have
to run on hardware which is poorly understood at best
He may be trying to argue that, but that isn't the central thesis of what he is arguing. His central thesis is that
[The brain's] design is not encoded in the genome
and that's just patently false. There's only one single blueprint for the brain and that's the genome. That the ways in which the blueprint is being read, interpreted and carried out are not in the genome does not detract from the fact that the genome is the blueprint. His arguments support the thesis that a blueprint is not enough. The objections to Kurzweil that I list are a summary/rephrasing of the arguments Myers provides. But he starts out by saying "No, that isn't the blueprint" and none of the arguments support that thesis.
Imagine going back to ancient Roman/Greek/Etruscan/&c times and handing them a ream of paper filled with the hexadecimal representation of an x86 application compiled for a Windows environment, and then showed them what it looked like when running. "Hey, look, now you can play videos and music!" Now imagine it was several orders of magnitude more difficult than that, and you're beginning to get the idea.
"If you could reproduce those 1 million lines and set them loose, allowing them to construct a human being..." The exact point he was making was that there's a lot of handwaved complexity in this statement, and that the abstraction "understand human being program, run code" is abstract to the point where it no longer accurately reflects the reality of the situation.