Apparently the co-op was actually playable on the show-floor. I'm not sure if Nintendo's really at fault here, Wonderful101 sadly seems to be a game that fails to get the interest of the press. Nintendo can show as much of the game as they want, when most outlets aren't going to cover it, the game's still screwed. That seems to be kind of what's happening here.
This reminds me of Keighley's Reggie interview. When he asked Reggie why Nintendo isn't showing new IPs, Reggie referred to Wonderful 101 saying they are putting a lot of effort into that game. Keighley on the other hand was simply laughing it off. The general consensus seems to be that people, in the press and among the gamers, just don't think that Wonderful 101 is very much newsworthy. They look at it for a minute and decide that it's not appealing to them. Wonderful 101 has a strange style, it's cheesy, it looks like some kind of Pikmin, it's combining all the ingredients of a cult hit with almost no market appeal. I don't think any marketing of the world can really change that.