I agree with these points, but what about the extra size of the eDRAM? Intel first eDRAM on mobile was in the I7 of 4th generation (22nm) and now on I5 and I7 of 5th generation (14nm) and AMD still using 28nm right? In a simple math if they had the same amount of transistors and architecture the AMD APU would be at least ~28% larger (against the 4th generation) and ~100% larger (against the 5th generation) so this is make it harder to add this type of technology, so they choose to and more Stream Processor and use faster ram.
I think that AMD should use this type of resource on their ZEN APU by the end of 2016 and beginning of 2017, which is rumored to be 14nm finfet.
This is a little to much, but who knows one or two HBM2 memory on the desktop line.