I understand where you are coming from. But I think it does have some value. When they grade a box, they are not expressing an opinion on the condition of the cards, just the vending box. It stands to reason that a beat up box is more likely to have beat up cards. Not a certainty, but a probability. Only you can decide if the premium is worth paying. Ordinarily I'd say no, but if they box was graded very low, I might avoid it.
I bought a non-graded vending box of 1977 topps baseballl and I did very well when I submitted to SGC....
Matthew T. Natale
Completed 1977 Topps Baseball SGC Graded Set, Average Grade 92.89