White dots on pizza or focaccia after baking

Sometimes I prepare a pizza dough that is a "direct" knead, no fancy preparations, works with all-purpose flour, rises in a couple of hours with regular yeast, about 70% hydration, olive oil inside.
It can be refrigerated after you roll out the dough if you want to bake it after some hours, with or without tomato sauce topping (I add the mozzarella later after tests in my oven).

In most cases, the fridge rest is about 18 hours. Sometimes I take the dish out about one hour before baking, sometimes I bake it right away (assume the oven is in temperature, about 250C).

No matter whether I let it rest before baking, I notice some white spots in areas that don’t have any topping.

I thought it was about the thermic shock of going from the fridge to the oven, but since it happens in all cases I really don’t see the pattern. What can it be?

Here is a picture of the final product after taking it out of the fridge where it had been for about 20 hours and a couple of hours at room temperature before baking.