Okay...let me recap. The chicken's head will be lopped off with an axe...including the trachea...it flops around violently with blood going in all directions...and it is in no danger of drowning in that process(????) but it is in danger of drowning while hanging upside down and the trachea is cut along with major vessels.
I've heard this theory before and I always chuckle about it. Blood is running down, not up. It gets into the nostrils and mouth of the bird, possibly occluding those airways...but~oh, look! it's okay because someone has cut the throat and trachea open so that the bird can still receive air!~ while it dies within 10-20 seconds.
Do me a favor, all who process, so you can attest to the validity of this assessment, try this method of killing and then inspect the bronchial tubes for blood residue and then tell us if this seems true: The blood cannot be sucked UP into the trachea and into the lungs enough to make a bird drown to death when the bird is hanging upside down. Even if this were possible, it could not be accomplished in the time it takes for the bird to die of bleeding out and the resulting cardiac arrhythmia. If the bird were going to drown because of blood near or in the opening of the severed trachea, could it not also drown because of blood in the nostrils and mouth of the bird with an intact trachea(it's all one airway)?
I've also heard Joel Salatin afficiandos stating that cutting the trachea cuts off oxygen to the brain and the bird dies quicker, resulting in poor bleed out....really? Wouldn't the lack of blood to the brain caused by the excessive bleeding cause the same effect...no oxygen to the brain? That's what is known as a tautology, I believe.
Let's use some logic...the bird dies within 10-20 seconds, on average...it cannot drown in that time frame, it cannot NOT bleed any more or less if the brains ceases to function due to lack of O2, it cannot do much of anything but die faster or slower(10 seconds vs. 20 seconds) in that time range, which is the desired effect..death that is quick.