Please refer to: https://pro.arcgis.com/en/pro-app/latest/help/data/annotation/annotation-feature-class-editing-properties.htm
As noted in the documentation above, certain symbol properties can be edited and still allow the features to maintain a reference to their symbol in the collection. For this issue, the list in the documentation has been updated to the list below:
- X- and y-offset
- Horizontal and vertical alignment
- Flip angle
- Font name, font style, and font variations
- Size
- Color
- Character spacing and character width
- Callout
- Angle
- Font—underline
- Word spacing
- Leading property
When these properties are edited the base symbol is overridden as seen with the update to the Override field.