Statutory authorities don't need be voted again; the government already has the authority to proceed with these expenditures. They are therefore included in supplementary estimates (A) to give a more accurate or more complete picture of the additional expenditures that the government plans on initiating. It's an enhanced measure of transparency to include these statutory expenditures in supplementary estimates, as they don't need to be there, per se. They're included to give a better picture, a more accurate picture, to parliamentarians.
On December 3rd, 2024. See this statement in context.