Some use it for E, others don't use it till F sharp. So it's still somewhat experimental. Manufacturers have come up with a standard hole size for it, a straight hole like a trill key with a fairly uniform hole size. And really, the opening of the key is so small that to make it work you have only got to make it leak. And, unless the key is well-made with strong metal, it bends.
Players tend to strain and squeeze a bit when they get to the top, and they just bend the key in.
So the third octave gets bent into the back of the second octave, and we regularly do this repair. At Howarth, we make the key thicker, a hand-forged key instead of a casting or anything else. It's not the perfect design, but then the oboe design isn't perfect anyway. And you do it primarily for export. At the moment it's still very small.