Exactly. I did research that as well for itod: https://bitcointalk.org/index.php?topic=766000.msg26795620#msg26795620

Like you said, when dealing with chaos, to receive X bits of your choice, you may very likely only have to change X bits in the input, regardless of the intermediate steps. In my research it's a loop of SHA256. The Private->public key computation serves just as well, hence the private key could be like 200 zeros followed by 56 or less bits of actual random data. It could be also Bacon26-encoded 10 random words from the English dictionary, whatever meets the entropic-I/O-shift requirements.