If the magma chamber never went through this phase, there would be no cool batholiths. At some point the rind must never again swell and break. Whilst I am tempted to agree with you, I am actually going to disagree - to make a point. I am arguing that closed systems cannot be assumed, and that there is plenty of field evidence to support the idea of openness. Even when solid, fracturing can continue, opening up new channels.
Solid granites have no shortage of channels for water movement.
There were just too many routes for water to escape. On this point, I think we are in basic agreement. The water travels so fast that it would have little time to cool on its way up. At these speeds, the water could come from a depth of 1 kilometer in 16 minutes. Here is my reasoning.