I don't think using AI generator is plagiarism...
Of course it's plagiarism. Plagiarism tools might not detect or classify it as such, but AI-generated content fulfills both conditions to be considered plagiarized.
1. You are using text that doesn't belong to you and which you didn't write. A bot wrote it.
2. You aren't posting a source from where or what you got the information from.
That's why it's plagiarism.
Just to add to that, AI generated posts is by all means a spam post in the regards that, your posting not because you want to but, because you are obligated to and source for assistance from some bot that might make posts that don't conform to the thread or perhaps it is a thread of its own but is of no interest to you that is making the post. The obligation just makes to either yourself or some attachment just makes you put it out there and that's not some good practice.
Haven't said that, the flaws in the system as alarmed by OP clears the air that these are not actual standards that is expected to work everytime but some speculative too to aid, in deciphering what could be from what ought to be. Not many users would be penalised out of this @OP.
Your conjugation and articulation @OP is cool and far from what is expected of an AI in the context of your subject which tells that, your use of English is good none the less.