Do you have an odd delusion that all other politicians *don't* require reporters to stick to pre-screened questions?
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Are you referring to the conference where the agenda was worked out ahead of time, it was about a narrow topic, and the positions of both parties and their objections were so predictable that either side could have performed in their sleep? It's not really that big an achievement, it would be more remarkable if he had failed.
We are talking about interviews, with reporters, where the topics can be far ranging, not about one single issue. How would Obama have performed if it wasn't just about the Health Care bill, but ranged around from Budget, to Taxation, to health care, To the Military, To Foreign policy, to Foreign policy involving Ireland and how it pertains to the Military, so on and so forth. That's why they *ALL* use pre-screened questions. To try and minimize Ambush Journalism.