Seems like they’re jumping the gun. GET isn’t scrapped. The guidelines say that unstructured or general exercise programs, or exercise programs based on fixed increments aren’t recommended, and they use GET as an example of an exercise therapy which uses fixed increments. So programs with fixed increments are bad, but tailored exercise (which most GET programs are anyway) is fine.
The description of exercise therapy sounds like any standard GET program: establish a baseline and then slowly increase exercise, but they do mention the energy envelope and the need to stay within it. And they say that patients should be informed of the possible risks and benefits of exercise, without explaining what they are, and say that some people get worse, some find no benefit and some do benefit from exercise.
The bit about managing relapses seems to suggest that relapses are to be expected and aren’t a reason to stop the treatment. At least the old trope about symptom exacerbation being a normal part of reconditioning is gone, but there’s no mention of stopping treatment if the patient gets worse either.
Given they say that exercise should not be recommended based on deconditioning, it’s unclear what the recommendation for exercise is based on? What rationale do the guidelines offer for why people whose core symptom is exertion intolerance should be undertaking exercise as a therapy, now that deconditioning has been discredited?
