It happens. I have one dog with a corked tail, but he's a suspected Boxer mix. His littermate brother also does not have a tail.
I've also seen the trait pop up in a few Sorrells dogs, apparently thanks to Sorrell's Red Lady Bug.
"No! If a man does not soon pass beyond the thought: "By what shall this dog profit me?" into the large state of simple gladness to be with dog, he shall never know the very essence of the companionship which depends not on the points of dog, but on some strange and subtle mingling of mute spirits." -John Galsworthy