Well, the problem is that using Artificial intelligence to create post is that it widely differs from the classic definition of plagiarism and the way it has been created for most of the history of humanity.
Only the source is different. With content stolen from the internet, it was easy to compare text A to text B to check if it was plagiarized because you could find the source. With AI it's different in the sense that the bot creates the content you ask it to. And even if you ask it to do the same thing multiple times, the outputs will probably be different.
Plagiarizing from AI is a new and non-traditional way. Other non-traditional ways are plagiarizing someone's speech. For instance, you listen or record someone speak on a conference about Bitcoin, and then you log into your Bitcointalk account and post that as your own. That's also plagiarism if you didn't make it clear that those aren't your words but someone else's and/or if you don't mention where you got the information from.