You're not looking at it from the right angle. Suppose that CP11 was a character that was completely out of left field and would drive the internet crazy. You really want to keep that character under wraps, but there's no way to absolutely guarantee the character won't leak one way or another. What else can you do to protect this information?
One way you can add another layer of defense to this is info to deliberately mislead the speculators with a fake "leak" that still has a hint of credibility. So in this case:
- Make the descriptions of CP9 and CP10 somewhat vague, but still accurate enough to match their reveal.
- Lie about CP11 by attributing false characteristic to it, but also include some true but relatively inconsequential information (i.e., the Mii costumes).
- Write whatever false information you want after the information you want to protect (CP11), but keep it consistent with the rest of the leak.
The speculators and the investigators looking for any and all clues they can find latch onto the credible info (the vague CP9 and CP10 hints and the Mii costumes), and then become primed to focus the rest of their energy around the false information down the pipeline. And the real authentic info becomes better protected because there's less people trying to look for it.
This is a technique known as "intelligence poisoning" and it's seen not just in business but also politics and military strategy as well. It's not so much a
fake leak as much as it is a
bait leak. The only reason most speculators brush this one aside is because Sakurai let the horse wander out of the barn when he said that there won't be any more fighters after CP11, which I'm guessing Nintendo's internal mini-CIA probably wasn't expecting. Had he not mentioned that you'd have a lot more people thinking the Rapper Mario leak was credible, rather than calling it out for the bogus that it is.