You don’t need the proof part if all the server nodes are trusted. Just the hashes is enough. I think that’s the part the author was pointing out in the article and we’re reading a bit too far into it.
If there is the potential of internal employees being malicious, then maybe trust isn't guaranteed.
I still don’t think the proof part is necessary even with the potential for internal employee tampering. With sufficient system authorization and security auditing catching someone tampering would be enough than wasting all that compute resource to prevent it for such a rare case.
Cool story though. I really like UO back in the day.