It’s funny when people who are skeptical AI use an AI checker that is also AI and believe its results 100%.

You're probably still stuck with old beliefs from when all available AI checkers were snake oil. Pangram is, to my knowledge, the only AI checker today that actually passes accuracy assessments. See e.g. on their own site: https://www.pangram.com/blog/third-party-pangram-evals

(Incidentally, if you asked me a few years ago I'd have predicted that reliable AI detection was impossible. I still suspect that it's impossible in general and that Pangram would break as soon as companies figure out how to make LLMs stop all sounding the same - but until then, it'll work fine.)