I don't think the pressure buildup will be a problem.
The stone is porous, so the water will release easily, preventing pressure from building up.

What would worry me more is if you put it in the dishwasher together with greasy dishes and other cooking utensils. A lot of grease willbe flying around in the dishwasher, and if it gets soaked up by the porous stone, I don't know how easily it will come off again.

I always lap my nortons on a DMT plate to return the surfaces to as-new.