I also believe longhauls and european flights are treated differently. European flights (from what I've heard) aren't edited that far in advance, and from my experience all upgrading is done by the gate. I'm not sure on that though, they might still do upgrades in advance on badly oversold european flights, and I've just never witnessed it.

For my part I stopped using the machine for oversold flights, just to be on the safe side. But I always use it when the flight is "wide open" or "just pretty full".