It makes perfect sense in this situation: we didn't have an option with an outright majority in the initial vote, so we've narrowed it down to two so that one of them'll be guaranteed to have a majority at the end of a vote, barring a tie. That said I'll add an "abstain" option for people who want to explicitly show that they're deferring to participate in the vote in the same way, as Bustos put it, you might submit a blank ballot at an election.