It means the studio can't endlessly meddle and tweak the show based on viewer feedback, rewrite scenes, promote suddenly-popular characters. They've essentially released a 13-hour movie that has to stand on its own. But it's a movie that can have logical chapters, tell a cohesive story, and give lots of room for character development.
Now I'm sure they did lots of pre-release viewer testing, but it still must be pretty scary for the creators. Fear isn't always the mind-killer - sometimes it sharpens the mind :)
(I've only seen up to episode 4 so far)