Bullet, Avenue, and Label all hold physical stock and move through PF Concept’s own warehouse network. WorldSource doesn’t. It’s the fourth world, and it runs entirely on custom manufacturing for large client projects. A PF Concept Shopify integration that treats all four worlds the same way ends up making a stock promise it can’t keep. Not a small bug. It’s the difference between a customer trusting your delivery date and a customer who never orders from you again.