I don't think folks out there are necessarily shitposting, or that there is some kind of "organised campaign" to put positive stories about CBT/GET out there. Those experiences are likely real, and there are probably more of them than we think. It's just that a lot of people keep quiet about getting well again because of the negative responses they get.
It doesn't mean they weren't really ill in the first place, or that they "never had CFS/ME" (I'll use it that way round because that's what many are diagnosed with). It just means that everyone's experience is different, and that we are still a very, very long way from working out what this illness is.
Unfortunately for us, many of the narratives have stuck - and the reason they have stuck is that provide seemingly valid explanations for many people. They fit with their experience, so that are taken as true. It's confirmation bias in action. And then it becomes a battle between whose "lived experience" is more valid. In a world where moral attitudes are mixed up with medicine, those who get well are always going to be taken more seriously than those who don't.