They're calling the lie on needing bleeding edge hardware for performance. 5 yr old silicon (14 nm!!) and no hbm. Their secret sauce seems to be an ahead-of-time compiler that statically lays out entire computation, enabling zero contention at runtime. Basically, they stamp out all non-determinism. https://wow.groq.com/isca-2022-paper
It's not really a lie though. They require 20x more chips (storing all the weights in sram instead of hbm is expensive!) than Nvidia GPUs for a ~2x speed increase. Overall the power cost is more expensive for groq than GPUs.
It's not inconceivable that's a better trade-off than leading-node and HBM requirements.