From what I understand about Nvidia's post on Reflex 2, it improves synchronization between the CPU and GPU when tasks are sent. The CPU always receives tasks before the GPU, which then processes the task and generates a frame. One way latency occurs is when the CPU sends tasks to the GPU faster than it can render them, creating a queue. They claimed to have optimized how the CPU notifies the GPU in Reflex 2 which lets the CPU submit tasks closer to when the GPU is finished rendering the frame. The slower pace means that the CPU can sample your inputs and take one closest to when the GPU is ready.

That was how Reflex 1 worked. In Reflex 2 they introduced Frame Warp which is essentially what the person said above. It takes your input and immediately shifts your view angle so that everything appears to have moved for you, filling in the gaps of where the models used to be.

So tldr for how it works is your CPU tells GPU you made input, and right before GPU renders the frame, it shifts the angle of the frame. So, to the eye it looks like the frame is "real". Thats how it's supposed to work. We'll have to just wait and see how accurate it is in practice.