bleeeurgh

It seems like the moisture detection devices provide Apple with a handy way to deny warranty claims for unrelated issues without the need to demonstrate that moisture is linked to the failure. A long time ago, I had an iBook that suffered the GPU failure that generations of Apple laptops were vulnerable to. The problem was clear -- I'd already had several other MacBooks suffer the same issue and get repaired -- but Apple denied service because of evidence of liquid intrusion elsewhere in the enclosure. After cleaning up the case and trying again, they were like, "yup, this is a pretty clearly another GPU failure."

Same thing with an iPhone X. Face ID stopped working less than a year in and since it wasn't a repairable part, they were going to replace the phone, but then they pointed to one of the moisture sensors being triggered and recanted. Even worse in this case, since the phone was advertised as being IP67 water resistant and phone had never been exposed to conditions Apple said to avoid to prevent liquid damage. So on top of the Face ID failure, the advertised moisture resistance was useless.