They address this in the conclusion

> How generalizable are these methods? Can they consistently deliver truly high performance? Can we get to a place where AI produces designs that maximize every conceivable trade-off, holistically optimizing every parameter to its most ideal physical state? .... AI can hallucinate a design that creates bad circuits that don’t work. This means verification methods need to remain under human oversight.

And they are essentially correct. We need better validation and verification methods, both software and hardware to keep in check the mistakes of automated random processes.