Testing for this issue included:
1) Verifying that the native file chooser is being used on Windows, Mac, and Linux.
2) Verifying that the native file chooser is being used for exporting an image, opening a file, and saving and loading of a session.
3) Verifying that the native file chooser are still remembering the last used directory and that they default to the user's home folder.
4) Verifying that the native file chooser will remember the user's last used directory upon restarting an IGB session, unless they reset their preferences, in which case the file chooser should default to the user's home folder.
Testing confirms that this issue is functioning as expected. Since the story is resolved it will now be closed.
I did notice that there is a problem if a user attempts to move a window that is behind the native file chooser. The portion of the native file chooser that was covering the window behind it will become "glued" to the window upon trying to move it. The window will return to its normal look once the native file chooser is closed.