I'm pretty sure this is a bug...

Course with 12 students
1 former student has attempted the quiz
1 current student has mad 2 attempts at the quiz

In quiz overview page:

Show students with attempts only: displays attempts of current student
Show all attempts: displays attempts of current and former students

• Show all students: Shows current students who have made attempts only. There are paging links to another page but no additional students are shown.
• Show students with no attempts only: No students shown. There are paging links to another page but no additional students are shown.

• Bugs?