One of the aims of shechita is to drain blood but it’s not the sole purpose of the practice. The legal literature even states that if an animal mysteriously releases no blood during slaughter the meat is still considered kosher. Although it must undergo salting to be eaten raw, something not normally required.
When an animal is shechted the heart quickly pumps the blood out of the body regardless of what position it’s in. This myth likely partially originates from the practice of hanging certain animals upside down during shechita. But this method of animal restraint, known as shackle and hoist, only gained prevalence because of USDA regulation and not kosher law. Additionally shackle and hoist is rarely practiced in the U.S. today.
Allot of backyard chicken butchers believe myth #7 and mistakenly assume that this is best way to drain the blood. They even avoid cutting the trachea and esophagus lest the animal inhale blood during slaughter. But this method often occludes blood vessels, stemming bleed out and delaying insensibility. Kosher slaughter strictly requires the butcher to attempt to immediately sever the esophagus, trachea and all major blood vessels. When done correctly this will cause massive blood loss and rapid insensibility.
Beheading requires the use of a chopping motion, which is one of the five movements that disqualify an attempted kosher cut. Additionally, such an action can cause extreme pain and would likely have a high error rate.
Some aspects of kosher production, mainly checking for sickness and the soaking and salting of meat, did provide a leg up for kosher production in the past but with today’s strict cleanliness standards kosher has little to do with increased hygiene.
While there might be some truth to this there is certainly no clear scientific evidence for it. If there is truth to it, whatever small health benefit might be gained from the kosher method would likely be far outweighed by other factors such as the way an animal is bred and raised.
This is a common myth about kashrut and while a blessing is recited over the act of slaughter this doesn’t need to be done by a Rabbi nor does meat become un-kosher if one omits the blessing.