Does calcium hydroxide react with citric acid in orange juice?
Don't know if this is the brand but here is such a label



Therefore calcium hydroxide is an actual additive. In this case advertised along with vitamin D (calcium fortification).

As for what gets to your stomach, there are reasons why ingredients, not compounds produced via cooking are listed. Cooking unlike chemical synthesis isn't supposed to create specific compounds, but food in which all compounds are mixed and every possible equilibrium happens at once. 

In the juice there's just more calcium cations and pH may be slightly affected, if it was significantly changed you'd find it by your taste.