Originally TweenCurves (started out as MeanCurve) was exactly that - Loft or Sweep the two curves together and extract the mid isocurve. The problem is that, depending on the curves, the surface doesn’t always loft/sweep as you would expect - as it does so by sampling and connecting equal division increments along the curve. TweenCurves simply added different ways of sampling the two curves for the connections, so you can try to find the optimal result.
The None option should probably resemble the basic surface method, the Refit probably resembles a loft or sweep with refit input curves and the Sample points will sample and connect an equivalent amount of points on both curves. Even then, it doesn’t always work that well with any of those options - it works best on curves that are similar in shape and don’t have “wild” deviations.
I agree that a "ThroughPoint option (with preview) would be cool.