Question, why is this marked as completed?

Because it is.

The main story is done. Now we are into the side stories and extras.

Oh I didn't know that was how it worked, cuz BJ Alex has side stories going on, but is marked as still ongoing. Thanks tho (づ￣ ³￣)づ

It's not consistent but at least if you Mark as read or reading you still get notifications if there are updates.