I would guess that it has more to do with stats than anything.
If you have a super strong application.....do it.
If you have a weaker one or some major red flags....maybe not.
I think that the reason when you apply is attributed to success is that who applies early is not necessarily a random thing. The people who apply early are the people who plan ahead, are driven, and are good with setting their own deadlines and following them.
These also are the same people who are more likely to have a strong application.
If your app is fine and you have the money, then do it. But be prepared to reapply (something you should be prepared to do no matter WHEN you submit your app) which means don't sit around and do nothing for the next 9 months.