I don't understand "100% recoveries"

Not to be that guy, but I can't stop thinking about this: How is it possible for people with PEM from LC, who have had it for years, to recover up to 100%? Considering that they (and I*😔) essentially have me/cfs, since having PEM for that long is the defining feature of me/cfs. 100% recovery would mean eliminating PEM completely and as far as i'm aware that's extremely rare with me/cfs. So did the people who recovered not have PEM, or was the PEM not established enough where they could escape in time? Am I missing something here?