I don't know Dave, it might be. I have done some "clever" experiments and have come to this conclusion.

Regardless of the settings that I can find, the generate curve option will create an initial extrude containing a curve of degree 3 and 1 span. It will be exactly 10/9 times as long as the diagonal of the extruded face. (Note I haven't tried it with multiple contiguous faces; that would be a more difficult calculation I think)

In order to lengthen the curve, you have to scale it up. Since the pivot point is at the start of the curve, this will produce the same result as extruding the face out further. You can then rebuild the curve with more spans and modify the curve, bend, etc. as necessary. I think I will go with this option. It is just a matter of controlling the extrude using the curve after it has been generated.