1) Create manual GB item in GBNG worth 100 points
2) Create Assignment worth 100 points and linked to the manual GB item for grading
3) Go to GBNG and score two students
4) Go back to Assignments and observe scores on Grades page (correct)
5) Click on a student submission with a score (points missing)
With an associated grade item (one that is created in the gradebook then associated when the assignment is created), grades entered in the gradebook now do not display to the student via the assignments tool, and there is no way for the instructor to release those grades (and their feedback) in the assignments tool, either. Thus the student will not see that their assignment has been graded and returned.
Note that the workaround is to exclusively grade these students directly in the Assignments tool. Then all release and grade push to Gradebook works as expected.