I ain't no expert (but I play one on TV) but looking at the general condition of all the tread blocks I would say it's defective. Is it only apparent on this one tire? It's called chunking. It usually happens off road or on harsh gravel roads.
I can see degradation for future chunking in the surrounding tread blocks. The hardest thing to get is a tire replacement especially on OEM tires. You would be better off (mentally) to either ignore it until the tire fails or needs replacing, or go ahead and purchase a set of tires you really want from a reputable tire dealer.
This is not a plug, just my humble opinion: I have been a Discount Tire customer for a lot of years and they always stand behind their products and take customer service very seriously. I bought a set of tires for my Civic and while the handle and wear nicely, they cause a lot of tramlining (wandering with the road grooves). Discount rotated and balanced them for free and even offered to "buy" them back. I haven't taken them up on it because they are relatively cheap tires. I should know better but I can't help myself sometimes. Plus I work too **** much and never get to drive my Honda anymore
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