Reporting widget on a Dashboard does not resize automatically when opening a report drilldown which is larger in size than the actual widget.
Responsive dashboards have the advantage that widgets can be resized either individually or by applying a quick layout. Resizing can be done only when editing the dashboard.
When not in edit mode, the dashboard layout cannot be changed. Therefore, when opening a drilldown, not matter the size, the layout will remain the same. The layout is not flexible outside edit mode and does not adjust according to widget contents.
When clicking onto a dashboard report widget type single score, the report drills down to show a pivot table. The table size is larger than the single score report. However the widget size does not auto-expand to fully display the pivot table, scroll bars appear in order to view the whole report.
This is the expected behaviour.