correct, elevated ESR is not a typical finding in ME/CFS, but there is nothing to prevent you from having ME/CFS and, say, RA (rheumatoid arthritis).
In the diagnosis-by-exclusion scheme, used in the typical (but incorrect) manner, if they found any other major disease which could cause fatigue (and which would cause elevated ESR), such as RA or Lupus, then you would not be able to be diagnosed with CFS (ME/CFS) under Fukuda.
Properly, if the other disease was fully treated and you still had fatigue, or if you had symptoms not explained by the other disease, you should still be able to be diagnosed with CFS under Fukuda. However, this is more complicated than it seems because Lupus, for instance, can cause all sorts of neurological and other ME-type symptoms.
We need biomarkers to be accepted for ME/CFS (Klimas' NK cells, Jammes' neuromuscular dysfunction, etc.).