I think he prefers it the exact same way. It's just not natural for him (and most people) to say nothing when someone asks him what he's working on. Even if it's just some small hacked together game he's still going to be honest. Most developers love showing off what they're working on no matter what it is because there's usually no downside. Due to his popularity, people go out and start telling everyone that Notch is working on this new super awesome game even though Notch is just fooling around with an idea.