When an assignment grade is set to Released the grade is pushed to the gradebook.
If you then set the grade workflow state to be one of the "non-released" states (e.g. In Marking) the grade and feedback part of the assignment continues to display the graded information as does the grade book.
I would have anticipated that if the grading workflow was changed to a non-release state it would be retracted from the gradebook.
It would seem that there is a predication that grade book updates only happen if the state is ASSIGN_MARKING_WORKFLOW_STATE_RELEASED (see /mod/assign/locallib.php gradebook_item_update() function).
This code appears to be the same in 2.7 so I'd expect the same issue occurs there