Computed columns for the EuiBasicTable naturally do not specify a field name to use. As a result, the generated key for the rendered EuiTableFooterCell is footer_undefined for all of them. Relatedly, if a table were to use the same field twice -- presumably with different secondary functions -- then it would hit the same issue with duplicated footer_${field} keys.

This leads to a warning per computed beyond the first one whenever the table has to re-render and it seems to cause some issues with React properly replacing the cell contents.