Hey pal, I grew up on a farm and we raised and slaughtered chickens.
Did you read the link? They are not killing the birds as they swing them nine times in total over their heads. The slaughter is done afterwards. The claim is that somehow by holding and swinging the birds by their wings it is less traumatic for them than swinging them by their feet. They are most clearly not swinging them by their necks.
Going down to see the slaughter of animals that are eaten for meat is probably a good thing to do (though gross, yes) in terms of keeping them grounded and appreciative.
Subjecting the birds to all those do si dos is just unnecessary and unkind.
Good grief! Let’s not scare the chickens!