I would suggest it is the passenger's responsibility to make sure they wake up and present themselves at the gate in time for a flight.

Whilst the attendant outside the showers will take your flight details and allocate you a quiet room and can be asked to wake you, I would be taking some personal responsibility to use your own alarm to wake up and make sure you don't miss your flight. By all means have the attendant wake up call as a second method but I would suggest it would be foolhardy to just depend on that alone.