problem is AMD have been using the VEGA as iGPU way to long in their cpu's.
It's been less than three years since Raven and we're looking at a power limited variant that is definitely not hitting peak clocks during sustained loads.
They have already done iGPU with RDNA2 for both SONY and Microsoft consoles, a SoC that actually are in production right now so it is not like they do not have the tech ready for release.
First of all how do you know the SoCs are already in production? They could very well still be in varying degrees of qualification but not final silicon.
Second of all, just because one chip is taped out doesn't mean they can just slice it down into another chip in one move. You expected them to have RDNA2 ready in an APU only 6 months after the launch of RDNA? And with all the driver bugs that RDNA has been suffering since launch?