Disagreements between Sony and Hideo Kojima were indeed growing around Physint, and journalist Jason Schreier revealed new details about the termination of their cooperation.
According to the journalist, PlayStation's decision was not sudden: the parties had been intensely discussing the future of the game, its growing budget, and its artistic and business direction for several months. The negotiations were supposed to lead to a compromise, although the disagreements proved too deep.
When Kojima felt that Sony was unwilling to finance a project for which a graphics engine had not even been chosen yet, he began negotiations with Microsoft, although PlayStation remained the 'financier' of Physint at that time.
Schreier also notes strong disappointment within Kojima Productions with how Sony made the decision. At the same time, both companies understood that disagreements were growing between them, and the project was gradually approaching the break-even point, so its closure was not a complete surprise.