The problem is which market is the target. 8 cores are useless in games and yeah the 6900k is not a gaming CPU. So if you want to built a workstation and benefit from 8 cores for lots of workloads, your point makes sense. For mainstream and gaming, not so much.
I'm concerned why the 4 and 6 cores have lower clocks than the 1800x for example. Is it binning or market segmentation? Does the 6-core OC worse than the 8-core (due to binning)? That would be terrible because then I need the more expensive 8-core to get as close to a 7700k in ST as possible. If I loose more than 10% In ST 1600x vs 7700k OCed the 7700k is the clear winner (at same price).
How long before system req for ultra settings will demand an 8 cores? AMD does work with game devs and those prices enable a large user base.
More cores aren't really hurting perf in a real world gaming scenario but can provide upside in some games that scale and will provide more and more upside.
There is also multitasking even if just gaming plus a light workload.
Ofc folks that want quad, can buy quad and maybe invest more in a GPU if budget constrained but that's not a good idea for high end.
Intel by staying on 4 cores has been trying to upsell gamers to faster SKUs and sites that test "gaming" with a Titan X at 1080p, have been helping them, intentionally or not by creating this illusion that you are gonna be CPU bound. Some folks will buy 4 cores Intel for gaming thinking it's better and they will get burned ofc. Staying with 4 cores is unsustainable for game devs as single core perf just doesn't scale much anymore.The only way to gain access to more CPU resources is to go above 4 cores.
The clocks might be about product segmentation for now and AMD could introduce faster SKUs, a technical limitation isn't the only possible explanation. And clear winner in ST has no relevance anymore.
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Dresdenboy
A bit offtopic, in that AMD presentation at HPCA, seems that a CU would have 32SP not 64SP , right? With 64 it would be way costly at just 500MHz while 32 and 1GHz sounds resonable.