They're just wasting their arsenal and time, it won't matter how many times that they fire rockets into the sea, they'll still be annexed.
I think the main reasons they're firing these "blanks" is two fold: 1. to continue their saber rattling and 2. to test their rocket technology while the rest of the world laughs in their face
eventually their rockets will be a true threat, and they probably won't test their nuclear warhead until that point