AI detectors are notoriously bad at actually detecting AI. I would not take those things at face value at all.

That was my impression in the past as well, but by all accounts pangram works well, at least at the moment.

It also seems quite plausible that it can be made to work by training on a lot of model output. Most of us already have become very sensitive to the various idiosyncrasies of model writing, after all. They have a very distinctive style.