I think that's a dumb reward that makes no sense. Suddenly, if you can play 1 song, you gain proficiency? I mean... I guess. Maybe. If you've been practicing it all Day, maybe you know the very basics.
But then, how'd you play the song to begin with if you aren't proficient? 2 Performance checks? Yeah. It's kinda weird.
I think it's implied that Alfira gives you a few pointers afterwards, even though it isn't shown.
Either way I'm glad I can obtain it in some other way that doesn't require wasting a useful feat point on, otherwise I'd never even bother with it ^^
