I think that makes sense. The ambiguity arose in my mind because Rule 6.2.3(1) refers to discarding an Influence counter. (I think the word "discard" is used because the counter is removed from play rather than being returned to the pool, although elsewhere the rules specifically say "removed from play" rather than "discarded".) Also, it would seem cleaner to simply say that at the end of an opium war, during clean-up, any remaining unused British Influence in player holdings is discarded (or removed from play). This would allow both Rule 6.2.3(3) to be deleted as redundant, as well as the final clause of Rule 6.2.2:
The player with the most British Influence commands the army. If there is a tie, all tied players will command the army. If any disagreement cannot be settled, then the war ends
and all remaining British Influence in player holdings are removed from play.