If you post something public it can be attested to by whoever that it once looked like X which is almost as irrefutable as it being self proving like a block chain. Scuttlebutt is trying to help you obscure your identity in posting and one could be sending encrypted content to particular other parties (maybe in its protocols but certainly just using it for the medium) where those parties could reveal irrefutably that content and that you made that content as that identity in that historical context.

Take instead the example of sending content encrypted with shared session keys over a live mesh network, where you send session keys to your specific friends to decrypt instead of revealing an identity to them.

Any "friend" could prove that they had some content at a specific time, but they could never prove that they didn't just make it themself since you gave them the symmetric key that let's either of you make shared content. This is a simple way to fail to achieve irrefutable though other properties as well..

If for example you are accused of a crime with no statute of limitations and a friend has since died, there should be a distinction between whether their hard drives prove something or their hard drives are hearsay without something else, like their testimony that they didn't tamper with contents in some long forgotten practical joke.