Generally there's either the experiential (e.g. do you hallucinate?) definition, which regards MDMA, THC etc as psychedelics or the receptor-based definition, which excludes them.
you can hallucinate as bat shit crazy from alcohol, does it mean it's a psychedelic? you can "hallucinate" in deep states of meditation, does it mean you took something?
I think that the notion that MDMA is psychedelia, is something which sprang up quite recently.
when I mean mind manifestation are the visions, patterns, realization, interventions, strong sensory "signals" you are getting by taking a decent amount under the correct circumstances.
personally, I don't like to speak about this subject, "this is psy and this is not psy", to each is own, but I strongly disagree about the term.
in any case, if it does good for a person, it does not matter what it is... it's just a problem confusing the two, since these are different groups with totally different outcomes.
edit, comment:
you will never see a full blown circus with upside down clowns juggling skulls and candy going on unicycles on a short pink white stripes roller coaster showing you the finger but in the other hand are very happy you are there, when using either MDMA or Ketamine.
I call the place shpongle land, been there several times, always happy to be back.