This bothers me...
But: On my recent narrowbody flights, I've noticed the FA's have been quite vigilant about this issue.
For example: I flew SEA-YYC, and we needed to ride a bus to the plane. So zoned boarding was no-go. When I boarded the Q400 (no J, but preferred seats at the front), the FA had closed the first 3 bins. The bins were empty, but she asked to see the boarding pass of everyone who tried to put bags in the front bins. So despite boarding half way into boarding, I still got my roller bag into the overhead above my row 1 seat!