I disagree. Only because sometimes I am interrupted and I haven't yet read all notifications. In that case, I'm not ready to mark them all as read.

Perhaps it should be clever then and only mark it as read when it's appeared on screen and you've scrolled past it.

And/Or that page should react and behave in the same way as the drop down. Allowing individual entries to be removed, or opened and so marked as read. 

I usually only use the "drop down" using the "bell" notification interface in both desktop and mobile.  However, I just checked out the page you mentioned.  I still would not want anything to automatically mark items as read--I want control of that.

With that setting, we're all different and options are a good thing.  I do agree that the notification page should have the same "mark as read" button/icon as the "bell" menus or, as you mention, an option in settings to mark items as read when scrolling.

Additional options and settings is always a good thing.