Leaving your seat belt is for your own protection against natural courses. It is not rectification for foreseeable injury caused by normal use of the aircraft (aka if they know the data is wrong 1.2 seconds ago, why did it use it 1.2 seconds later instead of the closest correct data to that point). That is a foreseeable problem for any reasonable programmer in their position designing that system. This is different from how it is not reasonably possible to make a perfect system.
There can be contribution from a person, but it would not be reasonable to expect a person to sit there for the whole flight never getting out of the seat. Also they did not add to the cause of the aircraft inflicting damage. It would be minimal contribution by the people at best.
Think of it like a car. If I make a case where it does not break under conditions because of a 0.00001P chance when the system could have been reasonable designed and foreseeable against this flaw, then the fact the guy is not wearing a helmet to stop head injuries is irreverent.