All they know is that one pilot was sleeping during cruise, they just assume it was the captain.
For some reason they are trying to make sleeping into a negative issue, something that may have contributed to the accident.
Catching some shut eye during cruise on single/double night sectors is a necessity and good airmanship. You sacrifice some alertness during cruise and transfer it to the more demanding approach and landing phase.
It's only a temporary fix if your roster is legal but extremely tiring. Having said that, I know naught about the AIX quality of rostering.