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).