It is true that what we term Astral Projection and Astral Travel are newer terms and it is also true that some people exploit these experiences for one kind of gain or another. However, the term the monks use are oneness and enlightenment and both of those things can and usually are experienced by people that are familiar with AP. Not the frauds, but people that actually explore the highest levels that they can of the mind - body experience. Now, not everyone that meditates experiences AP, but most people that experience AP do it via deep meditation.
Basically I think that people like myself that have the experience have a very difficult time putting a name to the experience. Most of what I have accomplished was very, very difficult to explain in words that could accurately describe how incredible and enlightening the experience was. So the best we can do now is use the name that gives a blanket covering to a wide range of experiences-AP.
The monks and even yogi's have different names for the same type of experience. Buddhist call it oneness or enlightenment. My experience of AP may not be the exact same as the Buddhist term oneness or enlightenment, but there are aspects that are the same.
I think it is the term AP that gives people a big problem, that and never having tried it or succeeded at it. So verre I will leave some links and a quote that might help you to understand a little more if that is in fact what you are striving for.
The Oneness of Body and Mind | Buddhism | Soka Gakkai International (SGI)
One quote from this article....
Modern medical science is only beginning to explore the subtle interconnections between body and mind, between the physical and spiritual aspects of life. Ultimately, Buddhism views both physical and spiritual aspects as vital manifestations of the life force that is inherent in the cosmos itself. As Nichiren wrote:
"Life at each moment encompasses both body and spirit and both self and environment of all sentient beings in every condition of life, as well as non-sentient beings--plants, sky and earth, on down to the most minute particles of dust. Life at each moment permeates the universe and is revealed in all phenomena."
Another link regarding the study and mri's of monks during meditation.
BBC News - Brains of Buddhist monks scanned in meditation study
So this brings me to a last point. maybe not your point verre, but one that may others have expressed. Is AP just a hallucination?
If it is...so what? Regardless of what you want to label it or critique about it, people that strive for it most often feel enlightened and like they have experienced something that very few others have. Having had both drug induced hallucinations and AP experiences, I would say they are very different and in some aspects the same. The only difference is that hallucinations NEVER gave me the cherished feeling of experiencing the greatness of humanity, an all knowing, all seeing and all accepting view of the world. Sure those experiences are brief and sometimes I cant remember what happened during what I call AP, but they are enough for me to feel that I am only a small part of something awesome.