This rule has been around for a long, long time. This is nothing I haven't said before and really don't plan on having to say again.
Seriously. Nearly everyone who starts one of these journal-style stories abandons it or gets too bored to finish, and then it's a mess we all have to clean up.
If you're going to write one of these, either wait and upload the finished product or honestly I can't say you should bother. Most of the new ones I am seeing are just depicting activity, and aren't particularly interesting.
If you do choose to ignore this rule, you will be given a week to finish the pasta, regardless of whether it is a journal or a story. No exceptions, no excuses.
It's edit grinding at its lamest. I would rather no one see something I haven't finished writing rather than show them a half-written, error-filled, partially-aborted thought.
It also makes us look less professional, in the least. It really angers me to see unfinished pages from July from users that still log in but don't bother working on them. I had one user tell me they got bored and didn't want to finish.
In short, these unfinished pastas almost never get finished out of sheer disinterest, and if they do get finished, they could just as easily have been posted when complete in the first place.
Post an unfinished pasta and have it deleted in a week, 1st time: Message on talk page, Post an unfinished pasta and have it deleted in a week, 2nd time: 3 days Post an unfinished pasta and have it deleted in a week, 3rd time: 3 weeks