I can't remember the times I was so dead tired and sleeping in the bunk and needed 3 calls to get me back on earth. Especially if You are in your first (REM) sleep, You might miss a call. You cannot blame someone who is sound asleep for that.
The relief crew system is based upon the fact that all normal and abnormal issues are handled well by the crew on duty. So short term problems and that includes a circumnavigation of weather and handling erroneous indicated air speeds. If that cannot be dealt with adequately, the problem does not lie in the amount of people in the cockpit.
If as a result of some failure or situation on board deems long term decisions necessary, it is time to get the boss out.
Reminds me of an old company story from the Constellation era that the relief crew ordered the captain to be awakened as a result of an engine shut down.
When entering the cockpit and assessing the situation he got furious, and while stumbling back to his sleeping quarters he was overheard grumbling G&*^%$ wake me F&*^%$^ up when another one $%^^# shuts down".
Only one hour sleep before the flight? Check today how much sleep right before the flight the crews have had when doing the early morning return flight from Asia back to Europe after a 24hr layover. It might be 7 hours. In total for the whole heavy crew.