Yeah, not a warranted item. They are wear and tear, like your tires. There have been a few threads on the beadlock bolt rusting issue. Those steel bolts don't have any special treatment or coating.
It looks like you take care of your wheels. But rust seems to always find a way - particularly for snow belt drivers. Exposed steel + water + oxygen = inevitable rust. And wheels take a beating from the whatever the road flings at them.
Solutions have been stainless steel bolts, black oxide bolts, Rustoleum paint, clear coat, and powder coat.