This issue is about naming state 9 and its associated functions and enum members. It also has a number of substates that need researching and naming.

Battle enters state 9 when the player or partner finishes their action. It seems to yield to whichever of (partner, player) has a remaining action, animates the switching of their positions if necessary, and, if there is nothing to do on the player team, it enters BATTLE_STATE_NEXT_ENEMY. See btl_state_update_9 in src/battle/btl_states_actions.c.