How do these chips work in games that hammer all cores? Something like Cities Skylines 2, which will use 100% of all cores once your population is high enough, is that hampered by parking half the cores more than it benefits from 3D cache? I presume it would be but I don't know.

I agree that a CPU with dual 3D Cache would be rather pointless for gaming. There is no way to eradicate the physical limitation of two CCDs so inter-CCD latencies will always remain a concern. And scheduling would be a real challenge because you would ideally always first want to "fill up" a single CCD before spilling tasks over onto the second CCD. That would be tricky in a game because the load usually isn't constant. It is variable so it would be really difficult to get it right while running the risk of latencies from hell in case the load is fluctuating or if CCD 1 needs to fetch data from CCD 2's cache or some latency-inducing fustercluck like that. Not good.

According to the source article at Hardwareluxx, AMD has considered a special edition (I remember that a dual 3D cache CPU popped up in shipping manifests at one point) but then reconsidered because it would be too expensive and that CPU simply would not benefit gaming as much as some people would like to believe.

IMO, a smart move by AMD. We are better off waiting for CCDs with MOAR COARS so we can get a single 12 core or 16 core CCD with 3D Cache (which will remain overkill for the vast majority of games).