Re: He inserted it the wrong way
Maybe not insert it the wrong way, but if you do something that damages it (like fall asleep while wearing them and roll over onto your side - putting pressure on it) that could eventually make a failure more likely. Or maybe crack the case so that water can get inside and short the battery - like say if you were working out and starting to sweat.
Perhaps we might start hearing about more of these over time as Airpods age and are exposed to more and more cumulative damage.