Well, that's the way the law was written for the end manufacturers. A supplier, like those that you buy clips, buttons, zips, etc, can tell you they have tested their supplies that you can buy, and you can use their testing results, but they don't really have to test anything, as they aren't marketing their supplies to children.
But, all of us end manufacturers are to be compliant. For a few to put CPSIA COMPLIANT implies that everyone else is not, which isn't true. God only knows what was in the heads of the commerce committee when they wrote this criptic law. They didn't ask but Mattel and the consumer freaks what to write. If you go back to the beginning of this law, the not advertising compliancy is the least weird of the law.