The not remembering symptoms thing is very relevant to me as I experienced this just this week,
I remember the constraining effect it has on my life like not being able to look out of a window, but not some of the specific details like a high frequency flickering of the vision when the eyes are closed. I don't necessarily see how its relevant to PACE though because gauging general level of health is not affected by that, it wouldn't change peoples ability to write down how ill they felt before and after participating in the trial.
Having had the sort of depression that causes 'fatigue' in the sense that people end up sleeping in the middle of the day, its easily distinguishable from CFS, its a coping strategy for extreme mental stress and complete lack of motivation, not a physical lack of energy, and those people would not experience PEM.