The difference between Hidden and Released is something I’ve struggled with a bit. My understanding is that if a column is:
Hidden and Not released: An instructor/TA can see the column in the gradebook (right????) but the student will not see that column in their My Grades. Useful for pop-quizzes, no doubt.
Not Hidden and Not released: The student will see the empty column in their grade book, but the instructor/TA can add the grades over the period of a couple of days. No students will see the grades until the column is released.
Not Hidden, Released: Students see their grades in the My Grades area.
I always give my Demo Student grades for everything, so that I can check visibility in the student tab. Gives me peace of mind.