Put your Doc Martens on, I don't want anyone to break a toe when I drop some science.
From a cocktail perspective, the problem with orange juice is that it's not very strongly flavored. Grapefruit, lime, lemon, and the various high-acid exotics all stand up to liquor just fine. Orange, tangerine, and their variants do not. They quickly become drowned out.
Over the winter I froze some satsuma juice.
What happens when you start to thaw juice is you wind up with this:
From a partially thawed container, I poured off the juice. Look at what's left in the container -- look at how much clear ice is there. You in the back, what's clear ice once it's thawed? Right, water.
So what we have in the measuring cup is concentrated juice, see, but it's concentrated without cooking anything down and boiling anything off: a lossless concentration, more or less. Technically, if you repeat this over and over again you can make a syrup -- you can make grenadine that way, starting with frozen pomegranate juice. There's quite a lot of volume loss, and it's a time-consuming process.
But a single run through the freezer? Think of it this way: you have just as much sugar, just as much acid, just as much of the flavor compounds, in less volume. You've removed water. When you add the alcohol of a cocktail, you bring the juice back up to its original volume, and you've replaced that water, that clear ice, with your gin and Campari, or your Aperol and genever, or if you're making a Union Club, your 2 oz bourbon, 1 1/2 oz juice, 1/2 oz maraschino, 1/2 oz Campari.