I've been cooking dry beans for years and I've always ignored the directions to carefully pick through the beans for debris.
This pebble was detected, thankfully, by my tongue and not my teeth.
soaking beans also helps remove farty oligosaccharides, which is why i soak them even though i have a pressure cooker
soaking them in salt water also makes the skins break less (i learned that the idea that they won't cook if they're salted is a myth. acid does prevent them from cooking though)