Dear @Hyeon.Cha,
The OpenFAST S-Function will use extrapolated values of the inputs (including blade pitch) passed from Simulink (as discussed in other forum topics e.g.: S-Function input output signal mismatch). Thus, the OpenFAST S-Function may not report exactly the same values of the blade pitch that are input from Simulink and the control signals should be smooth, without steps.
I’m not sure I understand your question about wind steps, but I’m a bit puzzled by your wind data anyway because I would not expect the rotor to be operational at such high wind speeds.
Best regards,