Importing an MXD with non-rectangular default legend patches into ArcGIS Pro converts the patches to rectangles and shifts the symbol for 'all other values' at the bottom.

Workaround

1. Open the map in ArcMap.
2. Save a copy of the map.
3. Select legend > Right click > Convert legend to graphics in the copy of the map.
4. Save the map, and import this map in ArcGIS Pro. This does not change the patches to rectangles.

Schritte zur Reproduzierung