While various post-acute infection syndromes may be lumped in the same category, they have differing pathologies & thus symptoms.

While there is a ME/CFS long covid subtype, there are many others as well. In other words, not everyone who has long covid suffers from fatigue.

It could be likely that the ME/CFS long covid subtype may share a common pathology with the varying CFS hypothesized pathogens(influenza, etc).

This is probably one of those areas where one symptom cluster (CFS) can be caused by several different things (COVID, autoimmunity, EBV, etc). So original causes may be different but they all converge on the same major symptoms.