Backdraft does 2 things that I can see. It creates a small channel through the surface ash so oxygen is available to the ember without having to pull so much air through the combustion area. The unburned bits of tobacco I have picked from the sides become part of the ember during the backdraft.
When the fire starts to die down, instead of only pulling air in, breathe technique is providing oxygen on both sides of the ember. Very gentle oxygen supply is the ticket. When taking a sip on a pipe, try opening your mouth to allow 50% of your intake to come from outside air and 50% to come through the stem and you will see the effects of "gentle air". The pipe will really start to cook.
Lessons from a campfire:
If you provide a lot of air (ex. blower), when you stop blowing it it tends to go out. Combustion was rapid but there was not a good base of coals.
To develop coals, you need the heart of the fire to stay hot. Fuel logs reflecting heat off of each other and keeping the core somewhat protected.
When smoking it is not good to totally exchange all of the air in the combustion area. Hence the term sipping a pipe.