If one sets up a course to use weighted categories (as in the video in the comment of
MDL-11835), and one fails to turn off "Aggregate including subcategories", no course grade is computed (unless each item is manually assigned a weight).
For that reason, I have suggested having this setting be changed to be off by default.
However, it is not apparent why this would affect the computation. And even if there is a reason, the computation should probably be changed to not factor in the subcategory or items unless a specific weight is set for them.