As per the discussion here: opensearch-project/OpenSearch-Dashboards#4279 (comment)

With the implementation of Data Grid as the component that powers the Table Visualization, the use case for Data Grid and the common size for Data Grid has been updated. Data Grid provides click-actions within cells to reveal truncated values, but there is no similar mitigation for when a row is too narrow to display the column header.

Therefore, another way to display column headers needs to be implemented. Tooltip does feel like the right approach on hover to reveal the column header. OuiBasicTable provides browser tooltips on hover of the column header while utilizing the entire column header string and the icon for the sort click action. It would be good to bring this pattern closer together across both.

Examples from OuiBasicTable: