I'm curious about this, as it seems to directly contradict (that which seems like) the common wisdom; pack looser.
The way I see it, you can only pack a pipe so loose before you're going to have trouble lighting it never mind keeping it lit. Plus, no matter how loosely a bowl is packed it's going to get compressed with tamping along the way. There's definitely more experienced smokers out there that can just stick a pipe into a bag of tobacco and come out with the perfect pack, but I'm not there yet!
Getting the tight plug into the top of the bowl while still having a good draw does take some practice with the APP method, but the entire bottom of the bowl stays empty for air circulation and moisture condensation. The function is somewhat comparable to how a Kirsten or H.Wiebe radiator pipe works, there's a regular briar bowl up top but a massive hollow internal shank/stem chamber where the smoke hits the metal sides of the pipe and condenses. This provides for a both a cooler and drier smoke by the time it reaches your mouth, ideally removing any hint of tongue bite no matter your cadence or tobacco moisture.
While the unpacked bottom of your bowl is nowhere near the size of a radiator pipe's internal chamber or as cool as metal (unless you're using a massive chimney pipe) I've found this packing method does prevent excess sizzling dottle at the end of a bowl and leaves a nice bit of moisture in the bottom of the pipe instead of in my mouth.
Plus, if you pack it a bit tight and are feeling too lazy to empty it out you can always gently poke a hole or two through the tobacco layer for added airflow, I do that with most folded flakes anyways. I'll stress
GENTLY though because if you're not careful that's an easy way to put a hole through the tobacco and into the cake potentially gouging your bowl.