Memories have their specialized processes indeed, but there are other reasons to specialize. New nodes are fine for logic, but it takes time for analog IPs to

Memories have their specialized processes indeed, but there are other reasons to specialize. New nodes are fine for logic, but it takes time for analog IPs to move to new nodes (and some may not). So what AMD did, using an advanced node for compute/logic and a less advanced one for I/Os should be typical. You can also see this in broadband cellular modems, where the baseband part is on an advanced node and the RF on an older one. When you look at processes offering, you often have variants optimized either for peak performance (frequency) or maximum efficiency. The peak performance would be the natural choice for (big) CPUs, and an efficiency node better suited for a GPU or any massively parallel accelerator where efficiency is more relevant than peak frequency (on this, I think Intel planned to use TSMC for their HPC GPU, could be related: they can focus on high perf for their CPUs).