Automated decision-making ensures completely objective incompetance. Large probability some on-topic postings will get hit. Newcomers unaware of identifier will be unable to post. Most if not all cross- posted articles will not get discarded. Difficulty in getting news servers to accept moderation of already existing group.
Spammers can and do forge approvals.
Servers which do not accept the moderation will continue to propagate spam. Propagation of messages outward tied to site where moderation is done. Would prefer creation of new group to moderation of existing one, but will probably grudgingly concede. Business as usual. Group remains unmoderated, spam continues to pour in unabated.