Honestly, I'm not surprised. It's pretty difficult to distinguish between different "grades" of pressure treating at the box stores and on the box stores' online sites and there may also be some variability in the supply chain that adds to the grins and giggles. Many of the folks in the store also may not truly understand the difference between "ground contract" and "buried" when it comes to treated materials. It's probably a good practice to source "in the ground" treated materials from a true lumber yard where you can specify the requirement and insure the best results.