Unexpected drill hole behind voltage regulator in EAGLE
It's hard to tell from the spacing but that hole is likely there so you can screw the regulator to the board, or more likely mechanically attach a heatsink.

You can see an example:



If there was copper you'd run the risk of connecting the tab to a trace or an internal plane.  This wouldn't work so well if your internal layer contained a power plane.

You should be able to find a vertical part in Eagle if you prefer the voltage regulator to remain upright.