And the PS4 Pro has some features from the RDNA architecture as well, if I'm not mistaken.
But it's still a bit weird that they mixed both aechitectures instead of going with a full RDNA2 chip. We'll see if the rumor/leak is true or not.
It wouldn't be surprising given the PS4/XB1 are a mixture of GCN 1.0 and 1.1 features. These consoles need to have their specs more or less ready at least 6 - 9 months before the new GPUs' designs are finalized, remember.