But it is worth repeating, that because the accident occurred just over 3hrs into the flight which is very close to when crew change would be occurring, we do not know whether the captain was just leaving the flight deck or returning. Arguments can be made for both scenarios.
PJ2:
So it is possible that the Captain set the course and left the cockpit for his break. And that the 1st officer remained on that course, not deviating to avoid the cells.