Dream, delusion, reality, drugs, schizophrenia, completely fabricated sensory manifold, whatever; the content does not matter for purposes of this question. Is that brain in a jar experiencing something? Is it experiencing at all?
That's consciousness.
Humans always liked egocentric views -- "The Earth is the center of the Universe". Or another version: "Humans are superior because they have consciousness".
If there are many levels of consciousness, one may imagine some extraterrestrial super intelligent beings that are many levels above humans, that would think of humans as non-consciousness beings -- like we think of many animals.
Now, if we go down instead, we can say that all animals with brain are conscious (just as not as we are), can't we?
In fact, I submit that it's the duty of anyone saying that the line separating "conscious" and "not-conscious" animals is here or there has to justify not just why that's where they drew the line, but that there is one in the first place.
The experince of having an experince can be wrong. If the existinece of experience is the content of the experience - and you have written that the content can be wrong. If one mistaken about the very fact of experience, is that valid an experience too?