Im gonna be the odd one (youre prolly used to it by now) and say, heck, why not..
It doesnt mean you're replacing the traditional way of grading books, just adding another tier. I can see how this would be effective for moderns and in a way, probably better for spec books you wouldnt care for much now.
How many modern non key slabs are out there on the market now which arent worth the the money, time & shipping of both sellers/buyers? Tons! That has a negative effect on the market. Now if you had the same books, with the same grade, without the case, I can see how more buyers would be inclined to purchase if the price was lower