That's called Fillet Brazing and it's Don Walker's specialty. This allows a custom frame builder to build a bike with virtually *any* geometry he deems neccesary for your particular body type and riding style. With lugs I believe you are limited to the angles in which lugs are available.

Custom frames aren't just for people with long arms or torsos or whatever. Everyone's body is shaped differently and everyone rides a bit differently, a custom built bike will be designed specifically for you and your riding style/needs. If you have the money for it there is nothing better.