Mine is like that as well. On most folding knives, that area really isn't all that useful even if it is sharpened (it's usually too damned thick to cut anything). I think ZT chose not to even sharpen it because it leaves even more metal at the base of the blade. If you flip it upside down, you'll see that in that area it has a nice amount of metal left on.
Also as others have noted, on many knives even where this area is sharpened, it is a nightmare to actually sharpen because the angle is ridiculously different from the rest of knife. I have a few knives with this area sharpened that the EP actually cannot do. The way ZT did this will allow easier sharpening...polishing that little area on most knives is a super nightmare to me, so I like how they finished it and I think the extra steel is a plus given it's added in an area that won't really impact cutting IMO.