The chatter marks in the wood are what is known as (planner outs)
Usually caused by dull planner blades. This actually is a defect in the product caused by the thickness planner machine at the mill. Sounds like a quality control problem by the supplier. The sawdust method will work, but you will still be able to notice a plemish unless its painted. Its a lot of money to pay out. I would agree with Csechman, return for replacement & maybe if they are reputable they will look after their mistake.
Also ask them if the wood is Kiln dried. Sometimes if the wood is not dry it will be hard to plane. Some suppliers will use a thickness sander which will avoid chatter marks. Moisture content should be around 18 to 19% for outdoor use.
Wood used for Furniture is usally 5 to 8% for indoor use. This would be to dry for a truck bed.

1951 Canadian Chev 1/2-ton Shortbox