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.
This has already becoming a debatable topic and I am also of the opinion that if you are using AI generated tools like ChatGPT to copy content and directly pasting it as your post it's plagiarism because you have contributed nothing in it so how come someone can believe he it's right to do so?
The AI tools also gathers information from the different resources and present you a text for the keywords you have entered as per your search but they also come from different authors so in reality you are copying someone work so it's violation of the rules.Some members do this just to earn merits but in reality they will be caught because we will have more such plagiarism detecting AI tools and moreover we can indentify to some extent the difference between AI generated posts and human written one's so there's no fun in doing so.