Hi Ronald, yes it's intended to work that way - it basically goes along with the overall focus in MoI on accuracy.

Most things in MoI work by trying to interact more directly with some specific geometry, like in this case the construction plane. Another example is when you do an extrusion, when you move the mouse MoI does not just map some amount of kind of arbitrary mouse pixel distance to some 3D movement, it instead tracks how close your mouse is to the extrusion direction line, that allows for things like object snaps to other geometry to generate an extrusion of the same height as other surrounding objects...

In the future it could be possible to have some option to enable the type of tweak tool method that you're used to, but if it just worked by moving in the view plane direction it's still quite easy to kind of tweak what was originally a planar curve like in your video to be nonplanar and that's often not good.

The focus in MoI for curve editing is more on 2D editing, I'd recommend switching to the Front or Right view (use the view tabs on the bottom toolbar), and editing the curve in that 2D view.

- Michael