It may come as a surprise to some here that the FAA is one of the few regulatory agencies that do not allow “controlled rest”… but like anything in aviation if the remaining pilot (or cabin crew) do not follow the prescribed procedures “controlled rest” can become “uncontrolled” and things like this happen. When I was overseas before the other guy took his controlled rest I’d go back and fill my mug with coffee, SOP was to call back to the cabin crew every 20/40/top of the hour (if we were more than 3 min late they would call us), we also had an Eicas message that if no one touched a button knob or switch every 5 min or so and if you let it go a few minutes longer it would become a warning and all the bells and whistles would go off.