My understanding is that when “Ranked Choice Voting” is described unqualified, it’s meant to refer to instant runoff.
As for the issues, they’re used to describe models of ideals in social choice theory. It’s true that the election only happens once. But think about it this way: imagine two alternate universes where, all things being equal, one voting bloc esteems candidate A higher than candidate B. In the other alternate universe, everything else is the same but the identified bloc esteems candidate B higher than candidate A. In IRV, candidate B could be the winner in the first universe but the loser in the 2nd universe. In general, monotonicity is the desire that being better positioned with respect to a given subset of the community (all else held equal) should better position you in the full social accounting. IRV violates this.
