If people aren't just wasting their time at Treasury Board, if the costing process actually adds value.... The PBO is suggesting it does because when they tracked the budget items from 2016, they said that for somewhere in the neighbourhood of 31% of the items, there was either significantly more spent or less spent than what was foreseen in the budget spending.
The question is, if there's valuable work being done at Treasury Board, why should parliamentarians not benefit from that work prior to approving funding, which is the norm, and has been the norm. The central vote authorizes a lot of money—almost $7 billion—because only $221 million of this vote is allocated so far. Those are the only things that have been through Treasury Board. Why should parliamentarians not benefit from a more rigorous costing prior to approving authority for program spending?