I don't think the CPSC is concerned with surface lead. If they were, millions of houses, schools and businesses would be off limit and condemned. That is where most lead poisoning occurs in children, from the paint in their homes. But those in congress forgot that little fact when they wrote this law. Writing "any" lead in children's products was down right insane.
How can a child be "poisoned" by the zipper on their jeans? They can't eat it, and I don't know of too may kids that go around all day dragging a pair of jeans and sucking on their zippers.
No, instead of concern for the lead paint in old houses, they worry about the snaps on a onsie's crotch that have an additional barrier of a diaper to prevent it from touching a baby.
The biggest concern in children's products should be in jewelry, the lead and cadmium in the charms and beads and chains. Children, even teenagers and some adults mouth these products, and children can swallow the parts. And the painted surfaces on toys that can flake off, and that babies and toddlers teeth on.
The valid testing for lead is by grinding up the product and disolving it in acid, thereby leaving you without a product to sell, just the bill for materials, shipping, and testing. But you have a piece of paper saying all was okay.