Maybe, but the board fired him without notifying OpenAI’s employees on a Friday before Thanksgiving week. Thats has to be more than a disagreement for such a forceful move.
The fact they timed the announcement actually implies some planning, which means the reason couldn't be so damaging that they had to fire him immediately after discovering it. (Of course, it's possible that only by coincidence, an unplanned revelation happened at a convenient time to fire him.)