1. Have a GB set up without Categories & Weighting.
2. Create multiple items and have them included in grade calculations.
3. Turn on Categories & Weighting.
4. Edit one item and add to a category.
5. Edit any other item. The checkbox for "Include in Grade Calculations" remains checked, but the box is greyed out and not clickable.
The item is not included in grade calculations, as the greying-out reflects, but the checkbox should not be checked.