In rhinoSdkGrips.h on lines 62-70 the following is found:
///////////////////////////////////////////////////////////////
// If true, then draw stuff that moves when grips are dragged,
// like the curve being bent by a dragged control point.
bool m_bDrawStaticStuff;
///////////////////////////////////////////////////////////////
// If true, then draw stuff that does not move when grips are
// dragged, like the control polygon of the "original" curve.
bool m_bDrawDynamicStuff;
I find from testing that when dragging a control point m_bDrawStaticStuff is true, and when not dragging m_bDrawStaticStuff is true.
It seems that the comments should be reversed (also in RhinoCommon by the way).