However, I was told a different story by the same source that gave me the Wii pre-order dates before GameStop gave official notice.
I got official word from the same source who's given our site exclusive breaks on several stuff, like the Wii pre-order date, that GameStop/EBX simply is not taking anymore GCN pre-orders for Twilight Princess because they are fearing a possible shortage unless more people convert their pre-orders from GCN to Wii. Not enough people have converted their pre-orders to the Wii version, and as such, they are expecting an extremely limited supply of GCN copies, so they removed online and in-store pre-orders to prevent an over-sell.
The GCN pre-orders will be done on a first come, first-serve basis, with online pre-orders taking priority over in-store. Online orders will be filled first, and remaining copies will be shipped to stores to fill in-store pre-orders.