To those thinking that they're going to add additional voices to cutscenes. You're being delusional, try to use common sense. It would be really akward and silly to backtrack and add voiceovers to cutscenes that people might have passed by now. If it was forgotten by mistake, sure. But then we would have seen a quick patch much sooner. The cutscenes without voices are intended to be that way. Most of the time because our character's name is mentioned in the dialogue.

I'm simply guessing that they're adding the files for the summer event with all kinds of fixes and small additions. It's what they usually do. Leaving them to just enable it, once the summer event begins.