I said Chronic Fatigue not CFS. If studies use overly broad criteria that include anyone who is tired then it compromises the validity of those trials. The name CFS is too easily conflated with fatigue as you have just demonstrated.
You linked to the Japanese study, which has myalgic encephalomyelitis/chronic fatigue syndrome in its name and, in the Methods section, said:
"Nine patients who fulfilled the international diagnostic criteria for CFS (
12) and ME (
13) were recruited from the Fatigue Clinical Center at Osaka City University Hospital, Osaka, Japan."
As
@Hip already pointed out, they used recognized ME/CFS criteria to identify these patients, so this was not just chronically being tired, which is different than ME/CFS.
I believe that true ME should be defined as those who have an adverse reaction to exercise or exertion.
Well, that's leaving a lot of important detail out. There are people who do not always have an adverse reaction to exercise or exertion who do have ME/CFS.