My exact same thoughts: the 7000HX parts are basically 7000X parts with a lower TDP and a different die carrier, no significant iGPU power to speak of, certainly nothing to match a 12 CU APU.
And what current iGPUs are able to squeeze out of ordinary DRAM is already amazing enough: to double that doesn't just require more transistors in the iGPU, you need either multiplying memory channels (Apple) or a very high bandwidth memory type to match that.
I've always thought one could replace one of the CCDs with some type of HBM for doubling the bandwidth for an iGPU. But then you still need some die area for a fat iGPU and the overall power requirements might not be worth the gains.
Some Apple-like play on replicating CPU/GPU/RAM blocks has obviously been proven possible and attractive with the fruity faction, but if you still need to support external RAM, PCIe etc. all those chunky high-power transistors currently on the IOD may just eat too much space to make that possible in a notebook form factor.
AMD tries to reuse their chip designs to the max and the TAM for something really fancy probably just isn't there for the budget prices we'd want to afford them.