I do not know how the rule is worded exactly - but I'm willing to bet it reads 'you have to hit your object ball first' this would mean an exact dual hit should be legal, if it says 'you cannot hit another ball first' then it would be illegal - sounds like random nitpicking...but there's a difference.
I first saw this in an essay a rather nerdy guy wrote about ties at first base in baseball. The rule in baseball says at first base the ball must beat the runner - therefore, in a tie, the runner wins. Funny enough - the rules also go on to say that at the other bases the runner must beat the ball....so the tie should go to the defense. When he raised this issue with the Umpire's association, the laughed at him and told him "There are no ties in baseball"
Just my random 2 cents.