I think the categories and the attributes assigned to them are fuzzy. That said fatigue that is attributed to CFS/ME is not just being tired, it's a whole other level, it is a crushing fatigue. CFS/ME fatigue also has clearly definable characteristics; for example Post-exertional malaise (PEM) that does not occur in depressed people unless they also have CFS/ME. In which case they're probably miscategorized.