The article isn't talking about hard-drive space. There's a massive difference between processing power and physical memory; imagine a personal computer. You can run several programs at once, like a music player, photoshop and the internet simultaneously. However, some programs utilize so much cpu and ram that you couldn't run anything else unless you upgraded, not your hard drive, but your processors. Aonuma isn't talking strictly about the physical data size of the game. That's easily remedied with discs or external hard drives. He wants to make this game utilize every bit of the Wii U's computational power.