Not necessarily. It's not like an image sensor where you throw it out if theres a single dead pixel. To increase yield of CPUs, they design them to have parallel redundancy and deactivate cores or memory chunks and sell it as a lower tier model. These AI chips are way more parallel than a CPU. They had decades of statistics of wafer flaw distributions before they began the design process, so they would design in just enough redundancy to get the desired yield for the process. I wouldn't be surprised if each processor has hundreds of things disabled (ALUs,memory units, whatever theyre using), and thousands to spare.
Traditionally, that has been the issue with wafer scale processors. Cerebras is supposedly selling these things to production customers for obscene pricing, probably offsetting the low yields. Who knows if it’s profitable though or still burning cash.