Draft holes are not only higher than need be, they are too small often, as are stems producing a less than adequate draft. This is why many open up the stem and draft hole and if need be, build up the bottom of the pipe. making a bad pipe good, a good pipe great, and a great pipe, SUPERB! NOT all pipe makers do this, But many do for reasons already stated. Sometimes it was just how they were taught. As you stated, you look at where the draft hole is located. Many do not. They also have no idea what size the draft hole is , or tenon, or shank. bit and there is more.This is one of the main reasons pipe gurgle. Poor air dynamics. All this means for me is, I have Great Respect for a good pipe maker or factory that produces good or great pipes. They are much more than the sum total of the whole.