I have been dealing with writers submitting AI articles, at least according to my trial version of Sapling AI Detection Software, and another free version. I test my own writing, and that of others I know are NOT using AI and it comes back clean.
When confronted, I'm told they have never had that happen before. I have no idea how to respond other than to say my software says yes, and I wouldn't have tested it had I not had suspicions.
I'd love to know what other editors are doing to prevent it.
I don't know how Medium can control it unless they purchase software for editors to use.