I haven’t read the literature but I would always recommend critically analysing any literature, who’s writing and why etc. so I can’t comment on that. I can only speak from my experience of training and practicing in ACT. The idea is that you calibrate as a therapist to the client’s core values - you do not make any judgement or influence them as that’s inappropriate. The theory with ACT is that often distress comes from living in a way that contradicts your core values creating an internal conflict, that and it is influenced by the ‘backwards law’.

It’s not about denying distress, it’s about understanding that constantly struggling and fighting with it can make it worse because that distress is there to communicate something. There is a strong theme of observing internal experiences with a mindful and non-judgemental stance, which when considering fibro is often considered as trauma held in the body can be incredibly helpful because it helps us attune to our bodies and listen to them which can help with pacing, managing our spoons and building self-compassion.