Key question in my mind is what is claimed. If nothing is claimed and the viewer assumes something, then the viewer needs to own their own bias. One could say that by not labeling the photographer is leaving out critical information but how much labeling is required.I think that "attracted" animals should be labelled as such, but there's more to it. If it's a simple portrait, then I don't think it matters much to the average viewer. Wildlife photographers may view it as cheating in terms of getting the shot, but the average person won't care.
Game farm and zoo / wild park animals are clear. Their own food source is their handler. What about habituated animals - wild animals that come to our feeders? Should they be labeled?
In the end IMO the photographer should not lie but also the viewer should ask if the issue is important to them. If the picture is "art" or simply illustrative then it probably does not matter.
If the shot is of the animal's behavior, however, I think the ethics are much more serious. If you see action shots of a animal doing something really interesting and think it's a natural, wild animal behavior, when it's actually been trained or enticed that's not right. A wild wolf won't sit or stand on its hind legs, but a trained one will. If someone sees a wolf doing that and thinks it's a natural behavior, that is a distortion of the truth.
On some levels, it may seem innocent (say an exciting photo of a jumping tiger), but consider what Walt Disney did for lemmings. Me and just about everyone I know grew up believing that they all commit suicide by throwing themselves off cliffs. This is not true, it was staged and edited to appear that way (see here), but ask 100 people and I bet 95-99 of them would say that they commit suicide. There are many other examples of this kind of distortion and some of it has been very harmful to the animals that are depicted. Fiction can be bad enough (consider the number of sharks killed senselessly after Jaws came out), but when fiction is presented as the truth, it's far more damaging.
If you label a show "wild life kingdom" or such, then you are claiming something.
I tell people that I have been licked by a wolf, which is true, but also quickly add it was habituated and use to being around people.
If a publisher / forum has rules about labeling then of course they need to be followed. If I show someone a picture of a xxx I let them enjoy it. If they ask, I tell the back story.
Game farms have a real use. I don't want 100s or 1000s of people out in the wilds stressing animals, perhaps causing them to abandon their young. No picture is worth the animal's life (or yours - but you can control the latter in most cases).
There is a fine line between game farms and animals that are free but are regularly feed/protected or baited. How do you honestly label the latter?