If I set grouping in OnStateInit, the GroupFooterTemplate does not have data for the aggregates I have set. If I group manually by dragging a column header, the data is there.
ADMIN EDIT: This stems from a framework behavior. The <GridAggregates> tag is a child component of the grid and as such, initializes after the grid. Since there is no event when all such child components are initialized the parent component cannot wait for them before starting to render and thus, it initializes before it can know what aggregates are defined.