This is a good point. The rulebook does say "When a hero resolves a battle action card, they may automatically defeat all delayed minions in their area before resolving the battle action step of the card" (page 5). I'd take this to mean you can defeat them before you get to the actual mandatory step of the battle card in the dark highlighted area, then you can decide to battle or gain 1 influence.
I'd be interested to hear others' thoughts on this too.
That is exactly my interpretation as well.