I have just tried your setup, the reason why it is not aligning the origin of PADS and Viewmate is that the gerber data will go out of the co-ordinate in to the negative plane region of your gerber sheet, since it took the extremes of your gerber data and aligned with the extremes of the gerber sheet.
you can go through the preview in CAM section before exporting gerbers to see how exactly your setting effect the location of the data.
best practice is to keep the origin in bottom left corner , and use "offset" as the justtification in CAM setup as david.ricketts suggested