My response assumes that you are talking about the "frame warping" feature of Reflex 2 (saying DLSS 4 was misquoting Nvidia's PR jumble) not simply frame-gen/MFG or upscaling. MFG, while producing even more interpolated frames, does not improve latency and will probably make it worse. I suppose an argument could be made for upscaling in a roundabout may (lower internal resolution = more frames = faster response time) but that would be more true for DLSS 3 as it has a lower GPU overhead than the transformer-based DLSS 4

Anyways, even if it were the case that graphic stack produces a response to the input by warping the frame during interpolation / before rendering, the input that triggers said response would (certius paribus) still go through libinput (and most likely the Wayland compositor) so timing would remain the same. For any features to improve on response time, it would likely have to circumvent one (if not both) libraries.