This may be happening in all of my folders, but I only actually notice it in this one. This is a freshly loaded view, and the list in the left panel has more sites/articles than the viewer in the right panel.
Also, note the top item in the right panel. I have not yet opened to view it and it’s already marked as read. Conversely, when I scroll to the last item in a folder, it does not get marked read when it hits the top of the pane. I am set to mark as read on scroll.
Windows 10, Google Chrome. Happens on all three of my computers.