See:
The roles weren’t “reversed”. Nvidia marketed their product using it first is all, but they’ve both been on board for years before it was made explicitly public. Unlike freesync for example, where they had to concede and start using it (albeit under some shady marketing term of course).
As for the main topic, I’m with @psycho_666, not the least bit surprised raytracing works on AMD hardware for the same reasons. As far as the numbers, last time I saw Nvidia’s numbers was on the Battlefield raytracing thing and that was around 30fps 4k with a 2080 iirc.
How do Nvidia’s offerings compare to the Vega 56 on this demo? If it’s the same then I’d say that’s a fail for Nvidia.