Hmm an AI answer I found says that the decoder only does 8k. Even on the newer XR2+. That would indeed be a huger bummer. Then again, it says the same thing for apple's M5. And that's not true.
It is possible that that AVP app's engine, does something smart, like a combination of hardware and software decoding. Or maybe the chip actually is way faster than those specs that I found.. Not sure what's going on. It's confusing for sure.
Here's some info on their tech: https://www.immersivecompany.com/platform
This sounds promising:
Prima is headset-agnostic and we’ve demonstrated our core technologies with partners across Horizon OS and Android XR. Please stay tuned as we launch on other platforms.
Honestly I have no idea how their tech works. I only know that it looks simply amazing on the AVP, far better than anything else I've seen.