The current intended behavior of Canvas is to show undated assignments as existing in the final grading period of the year. This was a surprise to many K-12 teachers when their Q4 grading period started as all undated assignments were now showing in their gradebook and on the student grades screen. Given the large number of assignments found in a K-12 course, this can really clutter up the screen. While this is the intended behavior of Canvas, I would not describe it as the expected behavior from the point of view of teachers and students.
This can be mitigated by Instructure in one of the following ways, or they can come up with a creative solution of their own:
Only show undated assignments when the "All Grading Periods" filter is selected. The downside is that teachers may be unclear about how those assignments are calculated into the Final average for the course. I would recommend adding an additional course setting to allow teachers to remove assignments without due dates from the Final calculation.
Provide users with a way to change undated assignments to "Not Graded" in bulk so that they are removed from the gradebook view.
Establish a new account setting that makes due dates required for all assignments that are not marked as "Not Graded". A tooltip that reminds teachers that they can set the assignment to "not graded" to avoid putting in a due date would be great if the teacher tries to create the assignment without a due date.