The shower and the gym get lumped into one risk. They're two, and they threaten different things.
In the shower, the stone isn't in danger. Soap and product residue sit on it and dull how it catches light, which washes off. The real risk is a soapy finger, which is how rings actually slip off unnoticed.
At the gym it's the stone. A hard knock at the wrong angle chips it, and that's toughness and cleavage, not hardness.
A soapy finger loses the ring. A hard knock chips the stone.