Don't underestimate the possibility of Satoshi being an anti-West nation state. They tend to have brainpower lying around, and have an enormous interest in curr

Don't underestimate the possibility of Satoshi being an anti-West nation state. They tend to have brainpower lying around, and have an enormous interest in currency systems they cannot be excluded from (see e.g. Russia's Swift ban.) By retaining the large initial chunk, they keep the origin and rationale secret. They also retain the ability to cherrybomb it as needed. Lastly, if the origin was known, there might be a push to get everyone to agree to invalidate their holdings via a special case.