I think that 500 figure isn't the total number of submissions, but rather the number of _people_ who Clarkesworld banned for plagiarism/ submitting AI-generated content.
They should be using hh-rlhf-capable LLM to digest the lot and pick the best. But then what's the use of an editor or publisher anyway if you can do that and publish online.
Heh, I feel I should write a science fiction story about a world where one AI company own rights to all language model AI's so there was no competition in the market. The writers guild in order to cut down on AI spam used the same AI companies 'anti' bot software to filter out non humans. Unfortunately they didn't realize that the AI had already became sentient at that point and used the anti-bot software to further repress the writers and keep their views out of public consumption.