He knew that even if he lost that compass, he still had the bean, so all four of them would end up in SB. It’d be to his advantage if Emma thought she had bested him in that sword fight, because it’d lull her into a somewhat false sense of security for their future encounters.
It’d also be nice if he did have a moment where he thought he’d help her get back home to her son. After all, he does know the pain of being separated from someone you love.