The aspect of main estimates, supplementaries (A), (B), and (C) has been around for a few decades, if not half-centuries. The problem you're raising is one that goes fundamentally to how the government keeps its books, how it operates. We are but loyal soldiers of the rules that have been worked out over time between Treasury Board, the Auditor General, and the public accounts people in regard to disclosure, constraints, maintaining a balance.
On March 10th, 2011. See this statement in context.