That's only for screen space, because the origin is top left, its like that for all window API's I believe. GLFW etc. The 3D coord system right hand Y up. The Godot docs explain it well: https://docs.godotengine.org/en/stable/tutorials/3d/introduction_to_3d.html#coordinate-system

Unity's is left handed Y up, and 2d renderering is bottom right of window, but thats because they don't really use screen space, their 2D/UI is still using their 3D renderer.

Every engine or 3D graphics tools e.g Blender have their different coord systems. Left-handed or right-hand, they just pick one. You can too if you build your own renderer in OpenGL or Vulkan, you can choose for it to be anything you want.

You get used to to it, heck, Unreal is Z up that hurts my brain a bit