However, they are grafted onto -- orange roots and stems.
Well, not quite. Poncitrus is a different genus, and is quite different from a true citrus. Poncitrus is often used as a rootstock because it is quite hardy...in fact, Poncitrus can even survive frosts down to USDA zone 6a. Unfortunately, they taste like crap, and despite attempts no one has been able to produce a palatable citrange (a Citrus x Poncitrus hybrid). This leaves them as a novelty for northern gardeners (yep, even if you live in a place with cold winters, you too can grow an orange, just don't use it for anything except marmalade...also they're thorny monsters) and as a rootstock for commercial oranges.
Not all citrus are infertile. It is true that the common orange, Citrus × sinensis, is a hybrid of C. maxima and C. reticulata, but it is not a recent hybrid, and it is a fertile hybrid. Some of them are infertile (sometimes this is the result of being treated with mutation inducing radiation, also unlabeled), but that's not really why they are grafted. Most fruit crops (with a few exceptions like papaya, watermelon, cantaloupe, honeydew, and some of the less commonly cultivated fruits like golden berry and kiwano, which all have short lifecycles) are propagated asexually, either through cuttings (like blueberries, figs, gooseberry, dragonfruit, and kiwis) or offshoots (like blackberries, bananas, and strawberries), but very commonly for larger woody tree fruit (and nuts) through grafting. This is done to get genetically identical crops. The thing with long generation crops like most fruits is that, unlike vegetables and grains, it would take many decades more than a breeder is going to live to get a tree that produces true to seed (in most cases, peaches kind of sort of do it). So if you plant a seed from an orange, apple, pear, mango, lychee, ect. you will get a plant, but just like the offspring of a person is always going to be different, the fruit quality will vary, and usually not for the better. This is the main purpose for grafting, although it is also used to speed the time to first harvest, and to impart specific traits to the crop, for example, dwarfing rootstocks are often used in apples, table grapes (Vitis vinifera) are often grafted onto fox grape (V. labrusca) for phylloxera resistance, and pears are sometimes grafted onto quince (an under appreciated fruit in a related genus) for dwarfing.
Now, if they were all sold as plain Gala apples, that might be different.
They are though. You are confusing bud sports with varieties. Bud sports are like varieties of varieties, so there's the original Gala, but there's also mutants that pop up every now and again, emerging from a single bud, hence the name. You've been eating those bud sports your whole life and probably never even realized it. Even notice color variation between two of the 'same' type of apples from different farms? That's not just environmental differences you're seeing there. A lot of things go unlabeled at the store. You never see blueberries labeled as Vaccinium angustifolium, V. corymbosum, or V. ashei, the three most common species of blueberry. You never see if a squash is the Daisey variety, or the Daisy variety (to commercial varieties of yellow crookneck). You never see that a tomato (Solanum lycopersicum) has for example the Ph-3 gene from S. pimpinellifolium for late blight resistance. I've never seen a watermelon juice containing produce state if the watermelons came from a diploid watermelon with the natural two copies of each chromosome or the triploid varieties, with a chemically induced additional set of chromosomes (made by doubling the natural two to four with a chemical like colchicine or oryzalin and then crossing a two with a four to get a seedless three chomosome containing watermelon plant that so many are fond of). There's an entire world of crop science that your average shopper doesn't know about and takes completely for granted as the browse the produce isle at their local megamarket. All this is the background context that is absolutely essential to understanding genetic engineering. This is why I am opposed to mandatory labeling. I want people to understand this topic. I work in this field, you you really think I want people to know less about what it is I actually do? Of course not. But a label without context, knowing full well how easy that could be to misunderstand in today's climate where there is so much FUD spread about the topic, is not the way.
Then there are honey crisp apples that are relatively pricey because they are hand pollinated (or something like that).
They're pricey not because of their pollination demands, which are no different than other apples, but more because of the high demand, that they are a relatively new apple, and that they are a bit of a pain to grow compared to some of the other apples.
It's not as if there are naturally occurring honey crisp apples and manipulated ones.
All Honeycrisp apples are manipulated. They were developed by the University of Minnesota in the 60's. Before that, they did not exist. An unmanipulated apple is hard, small, and rather sour, basically, a crab apple. It is certainty true that this genetic manipulation was not done with genetic engineering, but it is nonetheless genetic manipulation. If you look at apple diversity, you will see that quite a lot of manipulation has been done. You've got huge ones like Spigold, small ones like the crab hybrid Wickson, pink fleshed ones like Pink Pearl, sour ones like Granny Smith, super sweet tropical tasting ones like Snowsweet, all sorts.
We already do this with other livestock. So, what is so special about salmon to treat it differently?
I don't think we do. I am admittedly much less well informed about the animal side of agriculture, but I've never seen a chicken, turkey, cow, or pig product labeled as to what breed of animal it came from. To mandate labeling of this issue would be to treat it differently.