I was wondering about this myself - the properly drilled pipe.
No insult intended, but.... isn't this something that most manufacturers should be doing routinely?
It's like saying, "I prefer a Lamborghini because I like properly tuned cars."
What? Chevy doesn't?
Yes and no.
The difference between a racing engine and the engine in your car is a lot of tuning, for example the Ford F150 and 2017 Ford GT share the same block, but the GT gets twice as much power.
Except where this analogy falls apart is a Missouri Meerschaum 80 cent plastic stem does hit 99% of the performance you'd get from a finely tuned handcrafted stem, the only compromise is being made of a softer material.
Most factory Briars do start with an injection molded stem that could be crafted with similar design to a Missouri Meerschaum, but I assume they specifically choose not to make the draft more open just for the sake of durability, so there again the car analogy is applicable, any car on the road today could be tuned for twice as much power, but durability becomes a much greater concern.