Hi nos, here's a quick example to show you that "control points offset" does not produce an exact offset curve, except in the special case of line segments.

Here I have made a polyline and then produced an offset of it:



Then I drew 2 control point curves (with Draw curve > Freeform > Control points) and snapped on to the end points there, to make these curves:



So you can see there just by eyeballing it that there is not a consistent thickness between the 2 curves.

That's because an offset operation on a line structure is not the same kind of thing as a scaling transformation - applying an offset on just a line structure changes the proportions between the various segments - some segments become longer and some become shorter. Because a line offset produces that kind of changing internal proportions it also follows that just offsetting the control point hull of a curve will also change the internal proportions of the curve.

- Michael