Steps to reproduce the problem:

1. Create a course
2. Enable completion tracking
3. Create a quiz
4. Add a question (for example true / false)
5. In Quiz settings set grade to pass to 6
6. In Quiz Review options deselect all flag except "Overall feedback"
7. In Quiz Activity completion set Require grade "Student must receive a grade to complete this activity" and "Student must receive a passing grade to complete this activity"
8. Login as student and complete quiz and answer incorrectly

Expected feedback: "Done: Receive a grade" and "Failed: Receive a passing grade"

Actual feedback: "Done: Receive a grade" and "Done: Receive a passing grade"

If the teacher go to the Activity completion report, he sees on the student the green flag with the tip "Completed (achieved pass grade)".

I can also reproduce the problem on https://sandbox.moodledemo.net.

If the teacher now enter in the Quiz settings, Overall feedback, select the "Marks" options and Save, if the student refreshes the feedback page he can see the correct feedback "Done: Receive a grade" and "Failed: Receive a passing grade". I can then assume that the problem is related to the (deselected) "Marks" flag in the Quiz review settings.