Unlike your first source, this one does not even attempt to quantify what percentage of the variation in ME is explained by genetics. This only says that genetics plays a role. You need strong evidence to credibly state a monocausal explanation for something like ME.
The reality is that different biomarkers were discovered through the years by the Stanford centre by we are still looking for a specific biomarker to ME.
For example one of the criteria to diagnose ME is to have Pots, which is a disease with very specific symptoms.
Pots is a disfunction of the autonomic system and it is often associated with gastroparesis.
I repeat, you are endorsing a very obsolete theory about ME.
"Higher emotional instability was associated with both definitions of chronic fatigue and was confounded by shared genetics."
Of course, this theory is very unpopular with sufferers of ME such as yourself.