Fun fact: DWM enforces >1 frame of input lag on every Windows application running in a window. It is impossible to do better than 1 frame. But DWM itself does better: when you drag windows around they apparently stick to the mouse cursor exactly, which would be zero frames of latency. How do they do it? By cheating: they <i>delay</i> the mouse cursor by one frame, only while you are dragging a window. So the latency is still there but less obvious because it doesn't cause a difference between the cursor and window motion.
Mouse-to-display lag is even a hard problem in native desktop applications. TBH in this demo it doesn't look much worse than in a macOS, Windows or Linux UI application that renders through a 3D-API (and doesn't use all sorts of platform-specific hacks and tricks trying to minimize mouse latency).