Compact pickup fitment matters because a useful accessory has to fit the exact truck, share space with existing equipment, and support the intended load. A cover, rack, toolbox, or hitch can look appropriate yet block access, conflict with another part, or require mounting provisions the vehicle does not have.
A compact bed makes careful use of space especially valuable, but compatibility is more than a dimension check. Confirm the model year, body and bed configuration, factory equipment, and the accessory maker's approved installation. Then check weight, movement, electrical functions, and the way the complete setup will be loaded and used.