A pie chart does not adapt to changes made in the legend size properties.
Last Published: November 3, 2015ArcGIS for Desktop
Bug ID Number
April 14, 2015
November 24, 2020
ArcGIS for Desktop
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
The size of the pie chart in the legend is driven by the layer symbology settings. The legend patch size has no bearing on that, by design.