There is ZERO impact on APUs... MCM = Multi-Chip Module, which is most definitely NOT an APU or even an iGPU... it's an Intel CPU and AMD GPU married together on a single substrate. This simple gets rid of GPU PCB, as well as the distance between the CPU and GPU electrically, which should allow for lower latency between the two separate pieces of silicon.
The news article even explains how this works, so I'm very perplexed at how you came to this conclusion...
APUs are generally not seen as a replacement to a standalone graphics card. Instead, they look to replace the GPUs embedded on the motherboard. So it solves the distance problem and replace embedding GPU on the motherboard.