The Kirkland house brand is often backed by one of the name brands they sell. They have quality metrics for Kirkland and they check the products regularly. If the quality dips, they swap out the provider.
Hand tools variously came from many OEMs like SK, Plumb, Knipex, and Williams{2}. I suppose they still do, now at Lowes, but the OEM is Chinese.
{1}https://www.ifixit.com/Wiki/How_to_identify_who_made_your_Ke...
{2}https://forum.toolsinaction.com/topic/2118-craftsman-date-co...
If I want to return a product to Costco, I have really strong confidence that they will take it back.
Sears would exchange any broken craftsman tool for a new one even decades after purchase. Costco is much the same. Used, year old stuff with missing parts will gladly be refunded in full.