Coming from an MTV interview with Eiji Aonuma...
"When we were first working on the toon shaded Link, and that graphic representation of the Hyrule world, because it was such a drastic change, we actually kept it a secret from Mr. Miyamoto in the beginning. We had actually recently shown an example of what the next Zelda might look like, based on the 'Ocarina of Time' graphic style, and because this direction was so different, we knew that Mr. Miyamoto wouldn't approve it as it. So, I worked with my team to at least get it to a point where a battle sequence between Link and a Moblin would actually work in this world, and then that was the first time that we brought it to Mr. Miyamoto. That was only time we felt comfortable bringing it to Mr. Miyamoto.
It's not as though we were consciously keeping it a secret, but when Mr. Miyamoto would say, 'Hey, you got anything to show me?' I would kind of just push him off, and buy time as much as I could. But, at the same time, I think Mr. Miyamoto also understood that we were working on creating something, and just weren't ready to show it to him yet. Honestly, I don’t know how well we kept it a secret anyway."