Yes, ME/CFS seems to be one disease that chronic Borrelia infections may cause, but as you say, chronic Borrelia patients may have not necessarily have ME/CFS.
Personally I think the big mistake many people are making is not undertaking the appropriate testing for the enteroviruses associated with ME/CFS, namely coxsackievirus B and echovirus.
These two viruses are hard to test for, yet are probably the most common cause of ME/CFS (at least according to Dr Chia's
analysis). So if you have ME/CFS-like symptoms, you would want to test for all the viruses commonly associated with ME/CFS, including coxsackievirus B and echovirus, but also Epstein-Barr virus, HHV-6, cytomegalovirus and parvovirus B19.
Yet many people get tested for the herpesviruses (EBV, HHV-6 and cytomegalovirus), but neglect to get tested for the enteroviruses (coxsackievirus B and echovirus).
This is partly because the appropriate tests for coxsackievirus B and echovirus are hard to find: enterovirus expert Dr Chia found that only antibody tests by the
neutralization method (the ARUP Lab tests use neutralization) are reliable for detecting chronic coxsackievirus B and echovirus.
So while patients with ME/CFS symptoms fret about Lyme, and all the uncertainly involved in Lyme testing, they often completely miss arguably the most likely cause for their ME/CFS symptoms: chronic coxsackievirus B and echovirus.