They only need to be as good as the minimum standard for the category they're sold in. If you have a "good" bin and a "bad" bin, and the good bin easily exceeds the minimum requirements while the bad bin just barely meets them, that's fine, too. Or the good bin can be sold as class I, while the bad bin needs to be labeled as class II. Of course those categories usually aren't about safety-relevant aspects of quality, but things like weight or shape or appearance.