That seems to be A-OK as well, as Cortana, in all probability, has been fitted with a random number generator which can be called upon where there are situations which require you to actually make a decision – but are unable to simply because both choices on offer are those that you would want.
Right now, it looks as though such features happen to be available only on the U.S. version of Cortana, where some Windows Phone 8.1 users over in the US have asked Cortana to “roll dice”, resulting in a single die rolling around the display before it arrives at a particular figure. Mentioning “roll the dice”, however, would see a pair of dice roll on the screen instead.