Seems to change too often for a number station. I wonder if foreign intelligence agencies would even consider using an American company for their covert communications.

I think it is less spooky: My bet is on it being an iPhone app from years ago, maybe long pulled from the store. Its dev was using the Twitter account as a logging system. Maybe for something silly as highscores from around the world. "_dev" and "_prod" seem far too innocent names for an account that is trying to fly under the radar.

EDIT: Perhaps it is used for indexation benchmarks? Deploy a tweet with a unique string and location, and check how long it takes before it shows up in the index or notification inbox?