My regular SH is LGW- AMS

Most of the time all the Y bins are open and CE closed and the CC keep an eye on who is opening them and it’s a CE pax they quickly close them once the bag is in the OH

Other times they don’t do that and it then causes issues.

when I flew TAP the bins in J were closed and were monitored during boarding.

i was on a DL TATL once and someone from Y dumped their bags in the J bins and a member of CC saw it and removed them then a few minutes later paged the passenger to come to J which he did - probably expecting to have been upgraded - only to have his bags handed back to him and sent back to Y with him!