The point {0.5,0},{0.5,0} is not the same point as the mouse. That is bad. Please fix it.
Can confirm, happens in my game where a frame follows your mouse position.
I thought they addressed this, how did it make its way onto production lol
Scale is scaled to the usable area of the screen. That sort of makes sense.
Protip: The GUI screen space and viewport space are not the same thing. Luckily, Roblox recently added a bunch of goodies to the Camera to make this difference more clear.
The mouse when zoomed in should be where .5,.5 is.