I believe that the 'evidence' was a deduction from the cockpit voice recorder while the crew were waiting for the cargo to finish loading where both said they were fatigued and discussed the hours changes for pax as opposed to box carriers.
As UPS emphasized quite strongly the crew were coming in from time off! But that is precisely my point, there does not appear to be any acknowledgement that change in waking and sleeping hours causes symptoms that you could argue are not due to fatigue but they are precisely the same lack of attention, loss of situational awareness and cognitive tunneling. There should be some agreed method of moving to night operations after a period with normal days.