You are mistaken.
An AD (by definition) is caused by a mechanical failure.
I dont need to do a seach. I can do a search that results in a 22lr bolt with a sope being defined as an assault rifle.
But, most AD will only reslut in injury or death if the operator is negligent in the 4 safety rules.
Gun goes off due to an "AD", but it was pointed at someone in a negligent fashion (anytime it is pointed at someone you don't want to destroy, that is neglient), therefore the discharge and death/injury is a negligent discharge.
I have a friend that had a Walther with a de-cocker. He de-cocked it once and BANG. Prior to de-cocking, he intnentionally pointed it away from anything important, I guess you could call that RARE situation an AD.
I have a rifle I did a rifle basix trigger job to (not recommended), half the time I cycle the bolt, the firing pin drops full force by itself. That would be an AD, but since I know the gun has this problem, it is now ND.
IMO, mechanical ADs are so rare that 99.9% of unintentional discharges are Negligence, not accidents.
In light of safety, and personal responsibility for my actions, I would consider any weapon in my hands that goes BANG without me intending it to - neligent on my part. Mechancial or operator.