2010 9.9 Bigfoot 2nd drain hole in lower unit ?

[Mallard Machine]

Hey fellas just picked up a 9.9 big foot and noted there's a hole, looks drilled, opposite side of the drain plug. It's just into the open are where the water from the prop space lays. I've never seen anything like that before. Is it just a water /exhaust oil drain hole that mercury puts there or if that a custom job?