Exactly. It's just a study that reiterates the fact that EBV is a very key player in CFS. 20% is a pretty decent sized section, or sub-set.They said, "Using both serological tests and PCR, this study provided a robust finding of an active EBV infection in about 20% of the ME/CFS patients tested. The authors asserted that this finding indicated “EBV is an important factor for the development of the disease” in at least a subset of patients."
I don't think anyone believes that EBV is the cause of ME/CFS for everyone. I mean, you have the Craniocervical instability sub-set of CFS patients. You have those with genetic primary immunodeficiencies. Some have serious allergies, or major hormone dysfunction, brain abnormalities, all of which could contribute.