There are too many buttons available to an Instructor who puts new Assignments into Groups Sets. Because neither the Assignment Groups nor the Group Assignments nor the Group Sets come over during an Import, the Instructor must be cognizant that all the correct selections were made.
For example, my students are in groups. When I create a new assignment that I want to grade for a group grade, I must remember to select not only the Assignment Group but also select the appropriate Group Assignment. (Confusing, right?)
If you forget to select the correct Group Set in the Group Assignment box (even if you properly selected "This is a group assignment"), then the groups will not appear properly in SpeedGrader and you must grade each student individually--a problem because you must repeat not only all of the comments in the rubric and the grades--but also because the other students in the group did not submit so they cannot see any annotations (unless you download and attach the pdf, which doesn't automatically display sidebar comments).
Additionally, and most problematic, the instructor cannot see her Assignment Comments and attached files after she pokes the Submit button!
This is eternally frustrating and all because even though you told Canvas this was a Group Assignment, you neglected to select the appropriate Group Set. You cannot go back into the Assignment and Edit the Group Sets if any students have already submitted their work. WHY?
My suggestion: Figure out a way that an instructor who has yet to grade group work in Speedgrader can go back in and Edit the Group Sets.