ME/CFS is estimated to effect 2.5-5% of the population, that's not rare.
The author's claim that she is referring to "CFS" rather than "ME" should be enough to show that blog is highly irrelevant to ME/CFS patients. She's looking for a soft target where she feels more comfortable making quack claims.
There are many overlapping symptoms between ME/CFS, CFS, Fibromyalgia, Ehler's Danlos, even Chiari Malformation.
What many of these sufferers have in common is a methylation problem.
Patients had "CFS or FM" ... meaning an unknown number of patients didn't have CFS at all, so it would be impossible to guess the relevance. Fortunately the methodology is so poor that we don't have to worry about who the results apply to ... The selection process is not suitably described, so is not clear if the any of 88 "CFS/FMS" patients were found to have MTHFR variants before or after they were included in the study.
The questionnaires used were not good. One was for fibromyalgia, and the other states things in a very dangerous way for ME patients ... listing activities which are "impossible". Few activities are "impossible", they just make us very sick afterward, hence might be especially susceptible to bias. No objective measurements were used.
There is no information given regarding the calculation of statistics. No p-values, no effect sizes. And the one "significant" is used, it's impossible to tell if it's being used in the scientific sense, or as a layman would use it.
All of the patients selected to be treated (selection methodology not listed) had had many IV treatments involving B vitamins and high doses of methylB12 prior to being selected for the study. Thus the "researcher" already knew how they would react to much of the treatment protocol. And there is no indication of when baseline measurements were taken - at the beginning of the study, or at intake into the clinic before receiving infusions and being selected. There was also no control group for the treatments, which is especially relevant when receiving the treatment in a medium which itself can be a treatment, namely IV fluids.
In summary, the study which the blog's claims are based upon is complete junk.