From the Wikipedia page on orange juice:

> Commercial orange juice with a long shelf life is made by pasteurizing the juice and removing the oxygen from it. This removes much of the taste, necessitating the later addition of a flavor pack, generally made from orange products.

https://en.wikipedia.org/wiki/Orange_juice

The same article goes into additional detail:

> Commercial squeezed orange juice is pasteurized and filtered before being evaporated under vacuum and heat. After removal of most of the water, this concentrate, about 65% sugar by weight, is then stored at about 10 °F (−12 °C). Essences, Vitamin C, and oils extracted during the vacuum concentration process may be added back to restore flavor and nutrition.

So essentially there are components that vaporize during processing. The make sure to condense the same components and add them back in so that the orange juice contains all the components of fresh orange juice.

There is reason to think the differences are biotic vs. abiotic, between the two. Our digestive system is dependent on healthy microbiota. Pasteurization would be the difference here.

So it's essentially the same argument as for raw milk, but at least it's less likely to make you sick (?).

Raw milk is on the fringes of the same argument that whole foods play a more beneficial role in healthy gut microbiota and digestion, and that our current models focusing on nutrient composition are incomplete. It says that our measurements are off, and that there’s more to nutrition than composition alone. https://pmc.ncbi.nlm.nih.gov/articles/PMC11901572/

yes it’s been frozen and concentrated..

You can freeze and concentrate a substance without chemically altering it