Hi @solomon_klein - Interesting question, but I believe it's normal behavior, which I just repeated on a sample class.
The way you describe it, the instructor used the same quiz, but used the ability to add students with different due/available dates, as outlined here: How do I assign a quiz to an individual student? So, it's the same quiz, but by using the +Add button at the bottom the instructor assigned different students to different dates. The end result is that because it's just one quiz, the moderation page will show all students since--in the long run--all students have been assigned the same quiz, though with different due dates. As I said, this is what a sample had for me, and here is what the published quiz looked like:

I hope this makes sense and indeed describes the situation accurately, but if the above tactic was used, the Moderate page will have all students.
Hope this helps, Solomon. Stay safe!
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