Your Canvas Help Desk is incorrect. So, I will, for example, set up a course with the following Assignment Groups:
- Weekly Assignments - 40%
- Weekly Quizzes - 10%
- Exam 1 - 15%
- Exam 2 - 15%
- Final Exam - 20%
Within each Assignment Group, I pay attention to the number of points for each item. For example, each of the twelve Weekly Quizzes has 10 points for total of 120 points. Let's say the student earns a total of 96 points. Then for the "Weekly Quizzes" Assignment Group, the total percentage would be 80%
The Final Exam has two separate parts. The students first take a Quiz and then submit an Assignment. The Quiz is worth 10 points, and the Assignment is worth 20 points for a total of 30 points. Let's say that the same student earns 8 points on the Quiz and 16 points on the Assignment for a total of 24 points. For the "Final Grade" Assignment Group, the student's total percentage would also be 80%.
In this scenario, I pay attention to the number of points within each Assignment Group. I want all of the Weekly Quizzes to have the same number of points. For the Final Exam, the written Assignment is more important than the multiple choice Quiz so I have doubled the number of points the students can earn for the Assignment.
Your Canvas Help Desk simply doesn't know how to do the math.