This may be ignorant of me, but to me these graphs don't look all the different between controls and ME/CFS.
This is a good point to address.
The graphs obviously overlap. This is not as useful as finding something that is completely separated. Both for diagnosis or treatment.
Diagnostically it means you can't use the single parameter in question to identify ME/CFS sufferers. But it can still be useful.
For example, consider the role of height in assessing if someone is a man or a woman. The average height of men overlaps with the average height of women, i.e. it's not enough info on its own. But knowing the person's height helps! Especially if you see someone at a distance/can't see their face etc.
As far as treatment goes, a parameter that overlaps with normal people is obviously not enough on its own to cure the illness. If we find something that's 10x higher than normal people and we all have it, trying to get that down would be a priority!
But still, this points to systems that are on average working differently than in normal people, and suggests treatments focused on T-Cells might be useful.
In summary small differences are more like useful clues than breaking the thing open. But we are definitely still in the part of the investigation where useful clues are very welcome.