I have no experience with muscadines but vinifera, labrusca, and riparia can have fruit develop on primary, secondary and tertiary buds. In your pictures that'd likely be first, second, third, respectively. I also don't see any herbicide damage on the leaves. So I'd guess it's pretty normal to have fruit at various stages into the fall. If you ever have trouble ripening, hardening off, or overall plant growth I'd remove some/all of the less developed fruit.

We get those on vinifera often, we call them 'Christmas berries', becuase that's about when they would be ripe.

I learned something new today. Muscadines have self pollinating varieties and females that require a pollinator. I was looking at the new flowers and pinhead sized grapes and I was surprised to notice that my female vines don't have any. Only the grapes like the first and second pictures. The females don't usually bear as heavily as the self pollinators, but they are known for having bigger grapes. Makes sense since they aren't wasting energy on the hopeless late bloomers like the self pollinating vines. I've read research on muscadines from just about every major southern university and have never seen this documented in the literature.

Thank you for the post. I will check ours and report back. We just let ours grow on its own, though I should have been aware that cultural practice would change yield.