I could see the geometry getting updated for each parameter value. The final geometry and the results that you see correspond to the last parameter value in the parameter table.
I also tried selecting an intermediate parameter, set it as current and updated it. This updated the geometry as per the parameter value and displayed the results.
I think if the changes in the length is very small, then it might be difficult to easily notice the change in geometry. Can you try with higher length values?
Since this parameter is same as any other SpaceClaim parameter, I think it will get recognized in Optislang and Mechanical.