Naji, I think the simplest answer to your question is that Owen couldn't win by making the 1 ball, but he would most likely lose if he missed it. A lot of guys would go for the 1 ball slice, and the shot is makeable, but difficult; and it would be unlikely that the CB would break anything out of the stack that he could then shoot into his hole (absent a trick shot). Whereas there are 8 balls that go fairly routinely into Busty's pocket.
All these thoughts, and more, obviously went through Owen's mind. He elected to open up balls that he could make later, while freezing Busty in a very bad position, thereby completely turning the situation around for himself.
Doc