When it's a vision, it depends what you get to see. Often enough, what you see is not literally different, but its perceived meaning is different. Sometimes revelatorily different.
"Hallucination" is a judgmental term; it may be appropriate when it is involuntary, or what you see is harmful. People with schizophrenia have hallucinations, and (in all cases I have known personally) suffer for it. Thus, "hallucinogen" is a judgmental term about a chemical, where people taking one for the beneficial effects call it an entheogen.
The link literally does not contain the word “illusion”. It has no discussion about why the word “hallucination” might be preferable.
I’m not clear why you linked it, honestly. I fail to understand the jump from “astral projection” to “hypnagogic hallucinations”.
Was your intent to just say that sometimes the medical profession uses the word “hallucination”? That doesn’t give the word positive connotations, especially with laypersons.