Nope, not even close (at least in the United States). It varies a little by state, but in general defamation requires making either knowingly false statements, or having a malicious disregard for the truth, combined with intent to harm. An AI detection generator that gets a wrong answer meets neither of those requirements. You could potentially sue your employer or anyone else who took action on the false report, but the detector itself is probably totally immune.
Wouldn't having a demonstrably false accuracy rate, but simultaneously claiming to be 99% accurate in all circumstances constitute making knowingly false statements, and perhaps even malicious disregard for truth?
Public figures need to prove "actual malice" [0]. If you are a private figure, you need only show negligence.
[0] Actual malice itself is a term of art. It does not require malice in the normal sense. Just a reckless disregard for the truth.