Right, that's a different strategy again. If you're making a monolithic 64 core die and one of the cores is defective, and the next one down in your product lineup is the 48 core, that's going to make the 64 core model harder to stock (and maybe not worth aiming for at all, if your yields are bad enough that this happens often).

Meanwhile if you're making 6 x 8 core chiplets and one of those cores is defective, well that chiplet can go into a 48 core or be a midrange consumer cpu or something, and you'll just pick one of your many many other 8 core chiplets to go with the rest for the 64 core.