> Perhaps this alludes to all copies of DNA in a human body, which is much larger than 851MB.
I think you're being overly generous -- the OP clearly says "human DNA", and that fits the context of the rest of the post, which is talking about a single human. DNA that isn't human isn't human DNA.
The remarkable thing about DNA is that even though we have brain cells and nerve cells and liver cells and so on, they all have exactly the same DNA inside their cells, so there's no extra information there either.
