From owning quite a few of them, they are all drilled like that.Where did you hear that?
Not being confrontational, but it just looks like a regular mortice to me. I don't see a well. Draft hole is right at the top of the circle.
There is the mortise hole drilled down past the airway to fit the 9mm filter (the filter itself then sticks down past the airway like the tenon extension in a Peterson) and the turbulence drops the moisture as you suck the smoke up the filter. When you put an adapter in a bent Vauen the smoke just goes up the stem without dropping the moisture as intended by design. Bent it was never meant to pass a pipe cleaner with the adapter installed as they are meant to be smoked with an aktivkohle filter. The adapter forces the pipe cleaner directly down the center which doesn’t line up with the draft hole. This was never the intended route for the airway as I described above.
I guess I’m assuming you are talking about a bent pipe?