There are dozens of first generation AI detectors and they all suck. I'm not going to defend them. Most of them use perplexity based methods, which is a decent separators of AI and human text (80-90%) but has flaws that can't be overcome and high FPRs on ESL text.

https://www.pangram.com/blog/why-perplexity-and-burstiness-f...

Pangram is fundamentally different technology, it's a large deep learning based model that is trained on hundreds of millions of human and AI examples. Some people see a dozen failed attempts at a problem as proof that the problem is impossible, but I would like to remind you that basically every major and minor technology was preceded by failed attempts.