I also agree. As a beta test sight for C-H in my own home I had an 20a AFCI trip which I traced to a outlet in a 4x4 box just cramed with #12. The bare EGC had simply folded back coming into contact with the neutral screw. Although it may not have appeared to be hazard the neutral contact to the EGC allowed neutrsl currents to be turned loose and made available on all of the EGCs in my home which could have posed as a shock hazard for this those who may have come into contact with items grounded via the EGC as neutral currents intended to be insulted and isolated to the neutral conductor would have been shared with the EGC. The current on the EGC would be available even on water pipe providing a shock hazard to the plumbing system.
As such a tripping AFCI even though it may not represent a hazardous condition directly may be an indication of a wiring deficiency which would be worthy of a further review.
After varifying the integrity of the wiring then other causes for a trip could then be considered.
Anyway, that's my story and I'm sticking to it.