The "smooth scrolling" example in that tutorial is for precise scrolling with the stick, its speed depends on stick position.
If you need constants scrolling speed, simply enable ScrollTo behavior for your character (the one controlled with the gamepad). The screen will always scroll with your character.
If you want a smooth "inertia" effect, you can disable ScrollTo and add these events:
On every tick
-> System Set Scroll X to lerp(scrollx, Character.X, dt*8)
-> System Set Scroll Y to lerp(scrolly, Character.Y, dt*8)