The back of the Apple watch is also spending most of its time snug against your wrist, or down against a charger, while being relatively thick and uniform. It's not a 60cm wide, 20cm tall target for anything that falls on your desk, it's not made of 100 different, tiny little caps that all need to be light enough to not trigger automatically.

The conditions are _slightly_ different, and knowing your apple watch uses ceramics doesn't make you a materials engineer.