Here's something weird. According to one of the more reliable leakers...
Now DF did mention on their Hot Chips that RDNA 2 chip in the Series X did have some resemblance to RDNA 1 such as the Compute Units. I'll be interested to see whether or not the Ps5 has a similar configuration and more importantly... Whether or not Big Navi does. Take it with a grain of salt of course.
Was to be expected that it had some mix of different architectures, The GPUs of PS4, XBO, X360 and PS3 all were built in such a way.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454