In the past I would have likely written off such a thing, and I still question its relevance, since for severe sufferers with underlying biological complications, this will likely do next to nothing, and they will not even be able to participate.
But for myself, after 16+ months of hypnotherapy (which appears very similar to the explanations in the OP) I have little doubt at all these types of methods can play a part, but I think it is likely only for those with only a moderate condition but most likely those who have actually come some way in recovering and healing. I say that because I have no doubt at all due to the extent of suffering involved with this condition, that it leaves deep scares that could do with a little care, and we end up in such a serious 'survival mode' and just trying to desperately cope day to day, that even after solid improvement these mechanisms can remain.
Now to try and explain, based on my understanding, we are talking about neural pathways that become hard-wired and predominant due to certain events or habits over time, and with certain techniques they can be changed and replaced with more ideal ones.
I am still having difficulties to this day, about 2 years doing methylation treatment which I have no doubt at all has helped me healed, especially neurologically, but the therapy has also helped me work through the endless array of bad feelings from suffering so badly for nearly a decade and a half, and has connected me with feelings from my past I basically forgot I had; vivid clear summer days spent at my grandparents farm when I was 5. Its hard to hold onto them, but the more I work on it the more I get it back and are implemented into my day to day. Its no solution to all my problems, but boy is it nice to rediscover such things and generally be more at peace, more content with life and the world, and quite frankly it makes me much more comfortable, reduce symptoms and even helps me manage my energy better. It almost sounds stupid, recalling some memory from 3 decades ago, but when you continue recalling it, working with it and reconnect it in the brain more and more solidly, over negative impressions; its no joke and clearly influences emotion/biology.
Also doubt it is for everyone, your average person will struggle to participate with such things and avoid them, because going into your sub-conscious and digging around is not always fun; its generally better self preservation to maintain a practical mind set and try to just move forward. But the fact remains that everything that has happened to us in our life leaves impressions and much of it is all under there, and I think the physical suffering and trauma of all types of disease and illness can easily leave impressions long term.