Orient to View - This option is useful if True North and Project North are not aligned in your Revit project. If True North and Project North are defined identically in the project, then this option will not affect the way the import/link is oriented. The World Coordinate System (WCS) is used to orient the CAD file in the view.
If the current view is set to True North and True North is rotated away from Project North, then clear this option to align the CAD file with True North. If you select this option, the CAD file will align with Project North regardless of the view orientation. Note: CAD files are always imported into the current view from the top view direction. The CAD file is brought into the view assuming that the current view is a top view.
It also does something important or relevant when importing into elevation or section views. When people draw sections and elevations in CAD they are often doing so in the plan orientation of the file. It isn't all that common to see people reorienting their view in AutoCAD and then drawing those views oriented to Front or Back etc.
When we select this option and import such a file into a Revit elevation or section view it will rotate the plan of the CAD file into alignment with the section or elevation view. If not then the imported CAD file is aligned with the plan orientation of plan views and we only see the edge of the files lines in the elevation or section view.
If the option Current View Only is chosen then this On by default