Interesting concern...
In LOT Polish Airlines we have the demo tape recorded. When operating 3 F/A on 737 the purser is sitting and having coffee at the front( if tape recorder broken - reads the PA :-(( ), while no 3 performing in row 1, number 2 overwing exits, back galley left unattended.
In CentralWings, LOT subsidiary low cost, the same procedure as in LOT. Sometimes the purser reads the demo PA from the back galley, but it is always up to him/her. Hope this hepls.