Yeah... Nanjou isn't the real obstacle- he just represents a level of confidence in himself that Kyo needs to achieve and feel before he can finally admit to her how much he cares about her.
You see how shaky this kid is about things still? That unsteady voice, the fact he literally couldn't squeeze the words out for the rehearsal. He is not ready to proclaim anything as serious as a confession of feelings with the confidence he needs.
He needs things like this speech to make him realize that, yes, he is someone capable.
This doesn't require him to be 'on her level' or 'seen as an adult'- this is nothing so extreme. It's just capacity to achieve something that he should be able to do, but his current level of self-esteem does not allow. This will help. This isn't something arbitrary, it's something very vital to moving forward. This story doesn't really do arbitrary.