this evil Nintendo-news is sounding strange. Nintendo is gone good, remember? *shrugs*
So, why to do that? Because to avoid leaks and infos form 3rd parties? That is for me a good-sounding reason, but it is not good to do so.
But remember: Nintendo has been stolen upon so many times from M$ and Sony, that they even put their onlinegaming, price and controller behind closed doors. I think with that innovative demand they put upon themselves, it is vital to hide these things, as it will be no doubt copied and the property will be stolen (it has not to be, but may be!).
It is a bit strange not providing 3rd party with a single one bit of online-mode, maybe a temporal one as stated here. But that would mean to leave this online-mode in place for the whole lifetime of Wii. Once ready, always needed. Remember, they can not provide patches for a new online-support...