Auto Exposure ROI not working


I am trying to set auto exposure to work only for a particular region in the image.
Tried doing :
manager.zedCamera.SetCameraSettings(sl.CAMERA_SETTINGS.AEC_AGC_ROI,2, new sl.iRect(){x=0, y=0, width=1920, height=1080}, false/true); in unity.
This should theoretically work same as just enabling auto exposure if the resolution is 1080p. It does not seem to have any effect on the exposure. Am I doing something wrong or Is there anything else I have to do here?