I'm not disagreeing at all about refinement or the health. I'm just saying these refined substances are absolutely found in our kitchen, and used in quantity. They're nothing special or unique to processed foods.
If you bake bread or cake or brownies, for basic recipes it's nutritionally virtually identical to processed crackers, cookies, and bars.
And those sentences were likely in a larger context but chosen by the author as a way to say something the reader could relate to.
There is clearly a meaningful distinction between unprocessed and processed foods, as indicated by your example of apple juice, but by various definitions, apple juice is just a processed food, not an ultraprocessed food.
I don't want to claim that the popular concept of "ultra-processed foods" is super coherent, because I do agree there's not much sense in which a Twinkie is more processed than tofu or cheese. But there is a real problem that it seems like the researcher here is pointing at.
My impression is that they don't actually need to list "flavors" or anything special on the label when they do this, because they are just adding additional orange juice back, and it is highly unlikely that the result is nutritionally any different from fresh-squeezed juice.
The other argument for distinguishing ultra-processed foods is that even if the additives that wouldn't be found in normal processed foods aren't nutritionally significant in themselves, the resulting food is more palatable, so people consume more of it, but I don't think most people would say that bottled orange juice is more palatable than fresh-squeezed orange juice.
Anyway, it is theoretically possible that bottled "ultra-processed" orange juice is somehow less healthy than normal "processed" fresh-squeezed orange juice, but the point the parent comment was trying to make was that juice may be in itself unhealthy because the amount you consume is so much more than you would consume from eating fruit directly, and I was just trying to clarify that although true, this argument about juice in general is somewhat separate from the distinction between processed and ultraprocessed foods because fresh juice has that issue and can already be considered processed.
The meta point is that looking at ingredients alone doesn't really help much from a nutrition and health perspective. But also that nutritional science is a very inaccurate science as it's hard to get humans to actually obey studies and the digestive and energy systems of the body are "complex" systems, not just complicated. Any nutritional science is inherently flawed (or inaccurate) so the fall back of "eat like your 10k year old ancestors would" is safest from an evolutionary perspective.
This is my understanding as well. I believe it has more to do with creating consistency with the product because different fruit (and even the same fruit from different lots or seasons) will vary in qualities like acidity, brix, color etc. and consumers expect consistency. It actually becomes a fairly interesting operations research problem on how to blend various lots to arrive at a consistent product.
One way to think of this is that a food which is refined moves further and further away from the original 'real food' as it naturally occurs. ~80% of a wheat 'corn' is the white part, ~20% of a soy bean is oil, and 15-20% of a beet is sugar.
Similarly, one apple yields about 1/3c of juice. Drinking 2c worth of juice (in an hour?) is fairly common but nobody ever eats 6 apples in an hour