Subsets seems to be the conclusion.
While I agree that there are many subsets in the way ME/CFS symptoms are presented, I don't think that means there are many root causes. Even though there are many different "triggers", I think there is primarily one root cause.
Since ME/CFS affects almost every system in the body, maybe every system, (including the brain), it makes sense that symptoms would very, sometimes dramatically, from person to person.
A persons genetic makeup, diet, lifestyle, past infections-etc, (epigenetics) all shape a persons immune system, endocrine system and all other systems in the body. I think these genetic and epigenetic factors cause symptoms unique to that person, but with the same root cause in most of us.
Given these different presentations, I'm very interested in seeing how H.E.L.P. might help those of us with ME/CFS.