This is how chip fabrication works. It's how chip fabrication has always worked. Chip yields are never perfect. The lithography processes aren't 100% accurate, the substrates aren't 100% pure, and some portion of chips come out of the oven with flaws. Always. That's just how it is.

That doesn't mean those chips don't work, it just means they won't work to their maximum design specifications. So to use a very simplified example, a 32 gig flash chip with a flaw found in it somewhere can be burned so the flawed portion will never be used, and then binned as a 16 gig chip. A processor core that's not stable at its maximum rated speed can be burned so it'll be a perfectly serviceable lower speed version. Etc. The process is already done, the material is already used, and that chip can still be serviceable. So why throw it away?

That's the white hat version.

The black hat version is, some shady manufacturer could take the chips that are too flawed to be used reliably for any purpose, and use them anyway. Where that distinction is drawn is pretty important.