On Wayland, touchpad input does not follow screen rotation. When a laptop or convertible is used in portrait mode (for example, held like an open book), the touchpad directions are rotated relative to the display, making it impractical to use without an external mouse.
On X11 this is possible via coordinate transformation (xinput). Adding a way to rotate or transform touchpad input on Wayland would restore usability for portrait-mode laptop use and bring parity with touchscreen behavior.