Questions on cardinal and b-splines interpolation of ColorRamp


I am confused about the cardinal and spline interpolation of ColorRamp. Implemented in colorband.c BKE_colorband_evaluate function, I think Blender considers 4 nodes for cardinal and spline interpolation. However, when I used GUI and changed the position (or value) of two peripheral nodes, I didn’t see their contribution to the final interpolation value.

My setting is like the following: