Is this a bug of AP_SteerController?

In the function of int32_t AP_SteerController::get_steering_out_rate(float desired_rate)

The I term D term are using deg/s as unit, but the P term and FF term using rad/s as unit, as
_pid_info.D = rate_error * _K_D * 4.0f;
_pid_info.P = (ToRad(desired_rate) * kp_ff) * scaler;
_pid_info.FF = (ToRad(desired_rate) * k_ff) * scaler;

Is this a bug?

PS: When I am tuning the ground steering of a fix-wing plane, it seems the steering out put is not big enough, even I set the P items to 10(this is the max value allowed). then, I read the code, and found this.