Rob's Really Good Zero Grapefruit Zero

There's sugar in grapefruit, right? I mean I buy juices with no added sweeteners and there's always a decent amount of sugar in the juice, just from the fruit. The internet tells me that grapefruit has sugar, which makes sense, it's a fruit. According to Google half of a large grapefruit has 11.59g of sugar in it. So does Rob's somehow remove that sugar and replace it with erythritol, because the label on this clearly says there are zero grams of sugar. That would be some wacky science that just doesn't seem worth it.

I don't know how Rob's makes this, but this is tasty. It has the essence of grapefruit flavor without the extreme tartness. Sure it has a zero calorie sweetener in it, but it doesn't have a gross diet taste. I think the grapefruit flavor balanced it out nicely. My real question is was the erythritol really needed? Was it just used to round off the tartness? Only Rob knows and he's not talking. He's too busy with his Pirate's Booty (seriously one man, two great products. I'd give him a high five).