I, for one, used the term "bore hole" in the latter sense (the post's diameter didn't cross my mind).
With convection vaporization, since the load never really gets "packed," the major difference I notice between the flowerpot and an old school bong hit, airflow wise, is an
old fashioned is restricted enough in draw that it really needs the slide pulled to clear the chamber; with the Flowerpot I can clear the tube without even removing the heater. That offers a very comfortable, open airflow with minimal draw resistance, but that openness does affect vapor density to whatever degree.
It's subjective because everyone has different breath control, but since I like to use the Flowerpot with more oldschool beaker bongs and straight tubes, a more restricted airflow would help mimic the feel of a packed push bowl. I've used the showercap to achieve draw restriction, but on a 45 degree jointed downstem it's not super stable, and adds another element of hot mass to deal with. Lets just say when you have a big beaker bong in your lap, you don't really want a steaming showercap falling off... Been there!
Normally on a typical one hole combustion bowl, it serves as the airflow bottleneck, but since we need more surface area in our bowl for even vaporization of ground herb, airflow tends to increase there. Just a slight reduction in intake size in the heat exchanger would milk fatter at lower PID temperatures, and not place quite as much emphasis on personal breath control ability.
So why not just use a smaller pipe? That's certainly an option that works incredibly well, but after trying many shapes and sizes, I really do like the cooler vapor and nostalgic experience afforded by a larger water pipe. Something that "feels home" about it all!
Like my grandma always used to say,
"Home is where the e-nail is!"
.
Edwyn loves to tinker, y'know... 
