network – What ISP does he know about my local network when I use their ONU?

I have FTTP (Fiber to the Premises) and a UN GPON given by my ISP. I know that they can see the host names and MAC devices connected to ONU. If I connect my personal router to this ONU, then connect a PC to my personal router. Will they be able to see the host name and MAC of the PC connected to my personal router? When I go to ONU Admin Webpanel, I see only the router's host name and MAC, and the devices connected to the router are not the same.