Anything I'm missing here?
Yes. This part:
There also are certainly a lot of folks that actually *need* pro-level performance (a lot fewer than most of us, I expect) and not including an dGPU would lower cost (bringing the machine into the reach of a larger audience).
The CPU part that includes the iGPU that Apple wants to use actually costs A LOT MORE than the part that doesn't.
So regular CPU + dGPU is actually the same price or even cheaper than just the CPU that has that iGPU. Intel is charging an extra that'd be equal to the cost of a good dGPU.
Granted, it'd lower costs elsewhere (no need for cooling and extra video RAM), but the costs elsewhere are pretty minimal compared to the price of the CPU and GPU.