If it were the cause then all of the other diseases that I noted (and a lot more diseases and conditions as well) which appear to suffer equally from oxidative stress and lipid peroxidation - and therefore potentially reduced RBC deformability - should seemingly exhibit our same ME/CFS symptomatology, unless the impairment of RBC deformability is greater in ME/CFS or is somehow otherwise different.
There's an additional problem that I wasn't going to mention, and that is that oxidative stress is found in psychological conditions as well (which have physical underpinnings of course). In fact, a meta-analysis found lipid peroxidation in major depression (
ref), so chances are that (severely) depressed patients may show abnormal RBC deformability as well. An additional study would have to be done to see if that can be excluded and I'm not sure it's worth the money, at least not at this time.
It just seems that this RBC deformability issue is likely to be too common to be of much help for us other than showing oxidative stress is present. And we already knew that, although Dr Davis's methodology looks to be a lot more convenient than measuring malondialdehyde (a lipid peroxidation marker), for instance.