Heads Down, I have been told by a few people "in the know" in QF tech crew,that there is a huge difference between fatigue and being tired or insufficient rest for a duty.
If you advise your manager that you are "fatigued" then this is taken as a serious problem, you need to see your DAME (doctor) it is a more enduring nature, ie constantly tired.
Whereas if you report that you have insufficient rest because of noisy hotel room, insufficient slip time etc. Then this is a one of problem, and management shouldn't be able to touch you.
You need to be very careful about the terminology you use. Probably more so in cabin crew management.