You have subordered the B-spline variant under "smooth". I think, that is not
correct. If you draw a B-spline, your data points are not points on the curve,
but they are used as control points to form the B-spline curve. So a B-spline
curve is more like a Bézier curve. It is complete different from smoothing a
line with interpolation like in the case of cubic splines, which goes through
the data points.

People who know nothing about B-splines will be confused, what will become out
of there polyline. Those who know, what a B-spline curve is, will be confused to
find them as variant of a polyline.

The resolution of the cubic spline divides the interval between neighbour points
and you get different length, if the distance between the points are different.
For B-splines the whole range from first to last point is divided in equal
distances.

Therefore B-Spline curves are so much different from cubic splines that they
should get an icon beside the polyline variants and get a handling for them alone.