So one might look at the stacked cores as extravagant "L4" controllers serving their faster peers that might occasionally throw in some compute of their own for

So one might look at the stacked cores as extravagant "L4" controllers serving their faster peers that might occasionally throw in some compute of their own for particularly parallel workloads? Seems rather wasteful, but perhaps it's actually less bad than the performance per watt tradeoffs at high clock rates.