"Touch screen performance is very poor"
I agree, when scrolling or panning in games, the screen is lagging. Like every 200 millisecond scrolling will judder / slow down.
If enabling from Developer options Input: "Pointer Location", then scroll, it will show more dots while it is having the judder effect.
With inertia scrolling (after releasing the finger) it is smooth, so it is not about performance of updating the screen.