My take is that Peterson drills them like that by design. It's easier to drill a straight mortise and then an angled airway channel to the bottom of the bowl. The fact that it functions as a sort of halfway version of the system reservoir is a possibly unintended benefit. Both my Aran 01 and my Kelly XL02 are drilled like this, both have a tough time with a pipe cleaner, and both smoke great. Bottom line is it's just how they are.