I'm getting more confused the more I read into this. So the sleep dysfunction criteria is to evaluate whether we get PEM from over exerting ourselves?
No, it is there because when they analysed the literature they found:
"Unrefreshing sleep, or feeling as tired upon waking as before going to bed,
is among the most common symptoms reported by ME/CFS patients, and
only a small percentage of patients diagnosed with ME/CFS fail to report
some type of sleep dysfunction"
Page 86 of the report
and similarly on pages 210, 211
"The committee weighed several factors in reaching consensus on
these diagnostic criteria: (1) the frequency and severity with which these
symptoms were experienced by patients, (2) the strength of the scientific
literature, and (3) the availability of objective measures supporting the as-
sociation of particular symptoms with the diagnosis. Patient reports and
symptom surveys as well as scientific evidence consistently showed that
impaired function, PEM (an exacerbation of some or all of an individual’s
ME/CFS symptoms after physical or cognitive exertion, or orthostatic stress
that leads to a reduction in functional ability), and unrefreshing sleep are
characteristic symptoms almost universally present in ME/CFS, and thus
the committee considered them to be core symptoms."