It's one of those things that would make life a lot easier for us watercoolers.
For those of us that want to put the radiator flush to the roof, a reverse hole for a top drainport would make life a million times easier.
You pretty much can bypass the reservoir and it makes filling up the case a breeze.
I know the new swiftech radiators have the fillport toward the back, but not on the other side.
So simply put, 2 threaded holes on one side, like a standard radiator, but 1 additional one behind it for linking directly to a top fillport.