I don't know what ACC is.
If you're referring to Assetto Corsa Competizione, that game does not have RT. It was initially advertised as a game that would have RT added, but it never happened. Lots of games advertised RT when Nvidia came out with the RTX branding and then never actually followed through.
The game did get dlss added and has RT mods, but no official RT support.
But even if that were the case, a game being late to add support for cards that came out after the game did is a lot different than saying RT is sometimes exclusive to Nvidia. If there are any games that don't do RT on AMD, it's probably for that reason (that the game came out before AMD 6000 GPUs and the game was never patched) and that reason only. there won't be any games going forward that don't do RT on Nvidia and AMD, and Intel now too.
As for Protal RTX, it says it requires a dx12 dxr card, not an Nvidia card.
Nvidia wanted people to think RTX means ray tracing and that ray tracing is something exclusive to Nvidia. They made sure to get RT hardware out first so they could brand RT as an Nvidia feature, but RT is really a DX12/Vulkan feature first and foremost, the hardware came after RT was planned/created for DX12.
The term "radeon rays" predates RT hardware and was initially a software solution to make RT renders that would run on CPUs via OpenCL. It supports DX12 and Vulkan today, and it's hardware agnostics. There is no "RTX" vs "radeon rays" in games. There's just DX12/vulkan RT. So again, there is no reason at all to think a game will only do RT on one or the other unless it came out before AMD 6000 and was never patched to enable RT on AMD hardware.